(chiefly UK) A little island, especially in a river or lake.
From Middle English eyt, eit, from Old English īġeoþ, īgoþ, iggaþ, iggoþ (“ait, eyot, islet, small island”), diminutive of īġ, ēġ, īeġ (“island”) which constitutes the first element of island. See also ait.
English Wiktionary. Available under CC-BY-SA license.