island (n.) Look up island at
1590s, earlier yland (c. 1300), from Old English igland, iegland "an island," from ieg "island" (from Proto-Germanic *aujo "thing on the water," from PIE *akwa- "water;" see aqua-) + land (n.). As an adjective from 1620s.

Spelling modified 15c.-16c. by association with similar but unrelated isle. Similar formation in Old Frisian eiland, Middle Dutch eyland, German Eiland, Danish öland, etc. In place names, Old English ieg is often used of "slightly raised dry ground offering settlement sites in areas surrounded by marsh or subject to flooding" [Cambridge Dictionary of English Place-Names]. Island universe "solar system" (1846) translates German Weltinsel (von Humboldt, 1845). An Old English cognate was ealand "river-land, watered place, meadow by a river." Related: Islander.