An Etymological Dictionary of the German Language/Lauch
Lauch, m., ‘leek, garlic,’ from. the equiv. MidHG. louch, OHG. louh(hh), m.; comp. the corresponding OIc. laukr, Du. look, AS. leác, E. leek, with which lic in garlic is connected; a primitive and common Teut. word, which was adopted in Finn. as laukka and in OSlov. as lukŭ. Like most of the old names of plants and animals, it is of obscure origin. Gr. λύγος, ‘a pliant rod or twig for wicker-work, willow-like tree,’ cannot be allied on account of its meaning. Perhaps OIr. luss, ‘herb, plant’ (from *luksu-), is a cognate.