An Etymological Dictionary of the German Language/Annotated/Eiland
Eiland, neuter, ‘isle,’ from Middle High German eilant, einlant(d), neuter, ‘land lying by itself, island’ (compare Middle High German eilif, from Old High German einlif, see elf). Ein here has the meaning ‘solitary, alone,’ as in Einsiedler, Einöde. English land, and Dutch eiland, are not allied; they belong to Au; see the latter.