The standard dictionary of Old and Middle Irish dryly observes that the placename Lochlann exhibits variation in both form and declension . Its earliest citations are to Lothlind found in a marginal verse in a mid-ninth century copy of Priscian's Institutiones Grammaticae preserved in the monastery of Sankt Gallen in Switzerland :
Is acher ingaíth innocht
Fufúasna fairggæ findfholt
Ní ágor réimm mora minn
Dondláechraid lainn ua Lothlind
'Bitter is the wind tonight
It tosses the ocean's white hair
I fear not the coursing of a clear sea
By the fierce heroes from Lothlind'
and to Laithlind found declined as Laithlinne in the Annals of Ulster in 848:
Bellum re nOlcobur ri Muman 7 re Lorggan m Cellaig co Laighniu for gennti ecc Sciaith Nechtain in quo ceciderunt Tomrair erell tanise righ Laithlinne 7 da cet dec imbi
'A battle was won by Ólchobar king of Munster and Lorcán son of Cellach with the Leinstermen against the pagans at Sciath Nechtain in which fell Tomrair the earl, heir-designate of the king of Laithlind and one thousand two hundred about him'
In context both Laithlind and Lothlind clearly refer to the homeland of the early Viking raiders. Carl Marstrander identified Lochlann with Rogaland in Norway on the ground that Rogaland would naturally develop into Lochlann when spoken on the Irish tongue  but his argument does not account for the earlier forms of the name. David Greene considered all forms of the name and contended that it referred to a maritime centre of Viking power, that in its early forms it was an Irish name meaning 'marsh pool' and that interference from Rogaland and remoulding under the influence of the elements loch ('lake') and land ('land') resulted in a development to Lochlann and an identification with Norway from the eleventh century onwards . Donnchadh Ó Corráin later posited that it was in origin the seemingly unattested Norse name Loðland ('Grassy Land') borrowed into Irish and argued unconvincingly on circumstantial evidence that it referred to Viking Scotland but otherwise agreed with Greene that it developed into Lochlann under the influence of 'Lakeland' folk etymology and became identified with Norway from the eleventh century onwards . So while there is agreement on what Lochlann came to mean there is no agreement on its origin. In this respect it seems significant that none of the above commentators have properly considered a parallel usage in the early narrative literature.
In the early narrative literature the Otherworld is a supernatural place inhabited by supernatural beings. Its space-time coexists invisibly with that of the real world but just occasionally these hidden parallel dimensions open up to permit entry. Entry is usually unwitting being masked by unusual weather phenomena at an edge or margin such as a seashore, the rampart of a fort or the twilight between night and day. The beings found within are generally of human form being young and beautiful, wearing clothing rich and wonderful and dwelling in strange homes wrought from unknown metals though on occasion sinister species of grotesque and frightening adversaries are encountered. These various beings would seem to be artefacts of the gods and goddesses of the old pre-Christian religion reduced to mortality so as to accord with Christian sensibilities. Upon return to the real world the traveller often experiences a discontinuity of time and space, finding themselves hundreds of years or hundreds of miles from their point of departure despite having been but a short time away . Of present interest Lochlann appears as a northern/eastern overseas Otherworld inhabited by supernatural adversaries in the ninth century tale Cath Maige Tuired ('Battle of Moytura') , in the eleventh century tale Siaburcharpat Conculaind ('Phantom-chariot of Cúchulainn')  and in several subsequent tales. In rationalising this dual historical/narrative usage Proinsias MacCana held that the Vikings were likely assimilated into pre-existing Otherworld adversaries . Unfortunately MacCana proceeds from the restrictive premise that Lochlann was in origin the name of the Viking homeland and so somewhat forces his conclusion that the narrative usage was a borrowing from the historical usage.
Holding to the ancient idea of the earth as a globe lying at the centre of the firmament the medieval worldview finds geographical expression in the schematic mappa mundi ('map of the world') or orbis terrarum ('globe of the earth') in whose projection an O-shaped ocean encircles a truncated northern landmass divided into the three continents of Europe, Asia and Africa by a T-shaped body of water representing the Mediterranean, Hellespont and Nile. Distant lands are embellished with creatures and phenomena taken from readings of the ancient geographers, the Bible and classical mythology. The Fall, the Crucifixion and the Apocalypse coexist in an eternal now centred upon the holy city of Jerusalem. It is in terms of these maps and their eclectic mixture of reality and symbol that we should interpret a geographical text of unknown date preserved in the fourteenth century Leabhar Breac ('Speckled Book') which states that Lochlann extends from the Indse Orcc to Gothia to Datia to the Goethlaigibh Medotacda to Sliabh Rife and from Muir Chimerda in the south to the Uarda in the north to Aicen Sarmetecdai to Sliabh Caisp in the east and to Ferann na Cichloiscthi . When translated from Irish into classical and then modern geographical terms the text seems first to define a boundary extending along the northern edge of the known world of classical antiquity from the Orkney Islands to Gothia (Poland/Ukraine) to Dacia (Romania) to the Maeotic Marsh (Sea of Azov) to the Rhipaean Mountains (Urals?/Altai?) then demarcates a suitably vague area lying beyond by reference to the Cimmerian Sea (in classical myth a sea at the edge of the known world on whose shore lies the entrance to Hades) in the south to the Frigid Zone in the north to the Sarmatian Ocean (Baltic/Arctic) then along the previously given boundary to the Caspian Mountains (Caucasus) in the east and the land of the Amazons (in classical myth a nation of female warriors in Asia). To the extent that Lochlann is defined as somewhere other than Scandinavia the text would seem to be giving geographical expression to the narrative usage. A Eurasian Otherworld is first attested in the seventh or early eighth century fragment of a lost mythological cycle Immacaldam Choluim Chille ocus ind Óclaig oc Carraic Eolairg ('Conversation of Colmcille and the Youth at Carraig Eolairg') concerning the inundation of a kingdom by the waters of Lough Foyle . While sitting with some companions upon Carraig Eolairg, seemingly the rocky outcrop now known as Carn Iolair ('Hill of the Eagle') on the high escarpment to the east of the lough, Saint Colmcille enters into a dialogue with an Otherworld youth who brings esoteric knowledge from a distant past. Having learned that the verdant land the youth had grazed as a stag, ran upon as a wolf and lived upon as a human was now submerged by waters in which he had swam as a salmon and as a seal, Colmcille asks what lies under the sea outside the lough. The youth replies:
Fil firu fonnmaru foltlibru fóo. Fil búu uathmara alachtmara fóo asa mbind ngéim. Fil damu damdai. Fil ecu echdai. Fil déichendai fil trechendai i nEoraip i nAisia i tírib ingnath i ferunn glas asa imbel coa inber
'There are long-haired men with broad territories beneath it; there are fearsome greatly-pregnant cows beneath it, whose lowing is musical; there are bovine oxen; there are equine horses; there are two-headed ones; there are three-headed ones - in Europe, in Asia, in lands of strange things, in a green land, whose border is a border as far as its river-mouth'
At this point Colmcille interrupts and takes the youth to one side to continue the conversation in secret for half a day. When they part the youth suddenly disappears and Colmcille remarks to his companions that it is better that the living not know what passed between them. In this cryptic literary encounter between representatives of Christianity and the old pre-Christian religion we can see an early native tradition of an underwater Otherworld transform into the overseas Otherworld of later tales such as Navigatio Sancti Brendani ('Voyage of Saint Brendan') . This reflects the emergence of a new cosmology in which native lore was harmonised with classical learning by setting the Otherworld beyond, and therefore below, the aqueous horizon of a spherical earth . This Eurasian Otherworld with its supernatural adversaries ('two-headed ones', 'three-headed ones') extending to a rivermouth that can be identified with the Caspian Sea (then thought to be an inlet of the encircling ocean) can clearly be seen to provide a pre-Viking functional prototype for the Lochlann of Cath Maige Tuired, Siaburcharpat Conculaind and the text in Leabhar Breac.
Lochlann was the name given to both a narrative Otherworld and to the historical homeland of early Viking raiders. As no linguistic prototype of Lochlann is known to be attested in the Norse sources it would seem economical to conclude that both usages share a common Irish origin, leaving Lochlann as an Otherworld inhabited by supernatural adversaries in the far north brought horribly to life by the sudden emergence of Viking raiders from that quarter. Having sequenced the narrative before the historical usage (and so freed ourselves from the need to force a prosaic meaning such as 'marsh pool' or 'grassy land') it seems significant that the meaning of Old and Middle Irish words beginning laith- and loth- touch at a point suggestive of the mythological ale-vat of sovereignty (laith in the sense of 'ale', 'liquor', 'intoxicating drink' and loth in the sense of 'trough', 'vat', 'tub', 'vessel for holding liquid'). The ale-vat of sovereignty is an ancient motif with reflexes in the seventh century Irish tale Baile Chuinn Chétchathaig ('Ecstatic Vision of Conn of the Hundred Battles'), the Welsh tales of the Mabinogi and the twelfth/thirteenth century French grail romances in which a man travels unknowingly to an Otherworld hall and there meets a beautiful woman who as goddess of the land dispenses sovereignty as a drink from a golden vessel . The falling together of two words would go some way to explaining the observed variation in form and declension and so Laithlind and Lothlind are perhaps best harmonised as compound placenames displaying the very early adjective + noun word order laith ('ale') + lind ('pool', 'lake', 'sea', 'ocean') and loth ('vat') + lind ('pool', 'lake', 'sea', 'ocean') being alternate placenames for a body of water said to contain an underwater Otherworld in which sovereignty is contested with supernatural adversaries. This is an ancient theme with reflexes in the seventh century Irish poem Mess-Telmann in which a deceased prince of that name is said to have battled Fomoire ('Under-demons') living beneath the world :
Mál adrúalaid íathu marb
Macc sóer Sétnai
Selaig srathu Fomoire
Fo doíne domnaib
'A prince who has reached the realms of the dead
The noble son of Sétnae
Laid waste the vales of the Fomoire
Under the worlds of men'
through the eighth century Anglo-Saxon poem Beowulf in which a monster terrorises a king's drinking-hall from an underwater lair  to the enigmatic ninth to twelfth century Welsh poem Preiddeu Annwn ('Spoils of the Otherworld') in which the legendary king Arthur raids an undersea Otherworld to seize a cauldron . The development of the meaning and form of Lochlann as posited above can be represented in the following stemma:
Meaning/Form Time pool/lake/sea/ocean of sovereignty ancient | | Laithlind Lothlind | | homeland of Vikings 9th century | lakeland/Lochlann | Norway 11th century
While the earlier part must remain conjectural due to a lack of contemporary sources, the fact that the sequencing of the narrative before the historical usage allows us to resolve the two early forms of the name onto a specific narrative motif within a specific narrative theme makes for a powerful, simple and elegant solution. A solution, moreover, that renders the distant conjunction of theme, motif and place in Cath Maige Tuired and Siaburcharpat Conculaind (conflict with Fomoire, cauldron from Otherworld, Otherworld named Lochlann) as something other than coincidence.