An Etymological Dictionary of the German Language/Annotated/schleichen
schleichen, verb, ‘to creep, crawl, slink,’ from Middle High German slîchen, Old High German slîhhan, ‘to walk with a light sliding motion, creep’; ‘akin to Middle High German slī̆ch, masculine, ‘slime, mud,’ Dutch slik, slijk, ‘slime, mud,’ Middle English slîken, ‘to creep,’ with which English sleek and slick are connected; in the other languages the Teutonic root slī̆k (pre-Teutonic slī̆g) rarely occurs. — To this is allied Schleiche in Blindschleiche, feminine, ‘blind-worm,’ Middle High German blintslîche, Old High German blintslîcho, masculine. See Schlich.