Where does “slick” come from?

Slick comes from Middle English slike and sliken, from Old English slīcian, traced to the Proto-Indo-European root sleyg-.

slick (English): Slippery or smooth due to a covering of liquid;...

Definitions

Step	Language	Word	Meaning
1	Middle English	slicke	—
2	Old English	slīc	sleek, smooth; crafty, cunning, slick
3	Proto-Germanic	slīkaz	slick, smooth; sleek, smooth
4	Proto-Indo-European	sleyǵ-	to glide, smooth, spread; to smear; to creep; to...

slick — Etymology, Origin & Word History | Etymology Explorer