An Etymological Dictionary of the German Language/schlecken
schlecken, vb., ‘to lick, lap, be dainty,’ from late MidHG. slëcken, ‘to eat dainties by stealth’; allied to MidHG. slëc, m., ‘daintiness, dainty mouth,’ and havenslëcke, ‘glutton’; OHG. *slëcchôn, ‘to be fond of dainties,’ is wanting, as well as a corresponding term in any of the other OTeut. dials. Not allied to schlucken, but an intensive form of OIc. sl(illegible text)ikja, ‘to lick,’ which implies a Teut. root slī̆k, sloiq.