Meaning

adjective causing or tending to cause things to slip or slide

adjective not to be trusted; - James Agee

originFrom Middle English slipperie, an extended form ( + -y) of Middle English slipper, sliper (“slippery”), from Old English slipor (“slippery”), from Proto-Germanic *slipraz (“smooth, slippery”), equivalent to slip + -er. Compare also Middle English slibbri, slubbri (“slippery”) borrowed from Middle Dutch or Middle Low German slibberich (“slippery”). Cognate with German schlüpfrig (“slippery”),…

Etymology from Wiktionary, CC BY-SA 3.0