An Etymological Dictionary of the German Language/Schleife
Schleife, f., ‘slide; slip-knot, bow of ribbons, favour,’ for earlier ModHG. (still dial.) Schläufe, f., allied to MidHG. sloufen, slöufen, ‘to push, slip, dress’; also Goth. slaupjan, ‘to strip off’; AS. slûpan, ‘to glide, slip’ (E. slop), Goth. sliupan, ‘to slip,’ OHG. sliofan, MidHG. sliefen, ‘to slide, slip.’ The Teut. root slū̆p, from pre-Teut. slū̆b, contained in these words, has been connected, perhaps rightly, with Lat. (for *slûbricus), ‘slippery,’ and Lith. slùbnas, ‘weak.’