slippery (adj.)youdaoicibaDictYouDict
"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.
spar (n.2)youdaoicibaDictYouDict
"crystalline mineral that breaks easily into fragments with smooth surfaces," 1580s, from Low German Spar, from Middle Low German *spar, *sper, cognate with Old English spær- in spærstan "gypsum."