Slippery
wiktionary
From 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”), Danish slibrig(“slippery”), Swedish slipprig(“slippery”).
etymonline
slippery (adj.)
"having a slippery surface," c. 1500, from Middle English sliper (adj.) "readily slipping," from Old English slipor "slippery, having a smooth surface" (see slip (v.)) + -y (2). Metaphoric sense of "deceitful, untrustworthy" is first recorded 1550s. Related: Slipperiness. In a figurative sense, slippery slope is first attested 1844. Slippery elm (1748) so called for its mucilaginous inner bark.
