An Etymological Dictionary of the German Language/Annotated/Schleife
Schleife, feminine, ‘slide; slip-knot, bow of ribbons, favour,’ for earlier Modern High German (still dialectic) Schläufe, feminine, allied to Middle High German sloufen, slöufen, ‘to push, slip, dress’; also Gothic slaupjan, ‘to strip off’; Anglo-Saxon slûpan, ‘to glide, slip’ (English slop), Gothic sliupan, ‘to slip,’ Old High German sliofan, Middle High German sliefen, ‘to slide, slip.’ The Teutonic root slū̆p, from pre-Teutonic slū̆b, contained in these words, has been connected, perhaps rightly, with Latin (for *slûbricus), ‘slippery,’ and Lithuanian slùbnas, ‘weak.’