An Etymological Dictionary of the German Language/Annotated/Laus

by Friedrich Kluge

Laus, feminine, ‘louse,’ from the equivalent Middle High German, Middle Low German, and Old High German lûs, feminine; corresponding to Anglo-Saxon lûs, English louse, Scandinavian lús (plural lýss), Dutch luis, ‘louse.’ The word is common to Teutonic, occurring evelywhere in the same sense. The usual derivation of Laus from the stem of verlieren, Ver-lus-t, lose, löse (root lus), although supported by the analogy of Greek φθείρ, ‘louse,’ from φθείρω, is dubious, since Middle High German verliesen (properly ‘to lose’) does not occur at an early period in the sense of ‘to spoil.’ Neither is the derivation from the Teutonic root lū̆t, ‘to hide oneself’ (Old High German lûȥȥên, see lauschen), certain.