It appears that, after the initial settlement of the islands from the west, twenty-five to thirty generations ago there came a second wave of invaders and settlers from the east, in this case, Samoa. After that, the ancestral homeland was remembered as being in the east, and the islands of the west entered the realm of mythology.
At this point, it probably best to quote the exact words of Sir Arthur Grimble, from whom I am indebted for this remarkable legend. Any diligent readers I might have will perhaps recall other remarkable experiences he had related, in particular his encounter with a ghost, sorcery death, and most recently, a porpoise caller.
[T]he thought of falling too far to leeward of his islands in the S.E. trades became loaded for every Gilbertese mariner with a double horror. If he failed in his attempts to beat to landward against the mighty winds and sweeping swells of the navigating season (March to September), he was not simply a man forced to turn and run before the gale for a last desperate chance of safety beyond known horizons, but one already doomed to pass through dreadful fears to a yet more dreadful end in the abyss at the world's western edge.But, of course, someone must have been able to come back, or we wouldn't have such a detailed description of the process.
So as not to stray outside the limits - especially the westward limit - of safety when they navigated beyond sight of land, generations of fishermen and voyagers built up out of their experience a system of betia, or seamarks, by which, if only a man knew enough of them, he could be sure of his position in relation to any island of the Gilbert group. These signposts in mid-ocean might be shoals of fish, flocks of birds, masses of floating weed, or merely the way certain fish, or birds, or weeds behaved. They could be shapes of waves, or their size, or direction, or frequencies; they could be lines of driftwood, or shining streaks on the face of the water, or conditions of atmosphere, like high or low visibility, or even the smell of the air, ranging from land scents to te boi-n-anti, the 'stink of ghosts,' that told you how near you were to drifting to the western point of no return. Impalpable for the most part to any average European, these betia were as clear to the ordinary Gilbrtese fisherman as a bent blade of grass or the displacement of a twig underfoot might be to a tracker of the Australian bush.
The point of no return in the western seas was a betia called the Fishtrap of Kabaki, a scattered line of leaves and driftwood, said to stretch in the navigating season from the ghost lands in the far North-West south-eastwards to the latitude of Samoa. This line was the threshold of horror where the lost mariner first smelt the stink of ghosts. Beyond, the sea began to slope down like a river, its swift stream bearing him resistlessly westwards into a region of dead calms, where thronging voices whispered around him, "You are lost! You are lost!" and the monstrous uu-fish waited to suck him down. And if he escaped the uu-fish, the sea, ever more steeply sloping, swept him into the zone of wildfire, where a man had two shadows - one on the sail, one on the water - and green bubbles of light burst upwards from the depths to dance about his head, while the voices of women screamed for fear of a clutching Thing he knew to be very near but could not see. And if the Thing let him pass, then, for a day and a night, he was whirled through a zone called te-uabuki-te-re, 'the capsize-the-somersault,' where the ocean gathered itself in a last enormous race towards the lip of the world, and in the dreadful silence only the thin voice of a single bird was heard, wailing, "I kaawa . . .I kaawa . . . I kaawa! (I am unhappy . . . unhappy . . . unhappy!)" until the plunging waters flung him out with his canoe, over and over, down, down, down into the black and bellowing abyss of Mone.
Reference: Arthur Grimble, 1957, Return to the Islands, John Murray, pp 50 - 52