Slicker

google

ref

Middle English (in the senses ‘glossy’ and ‘make smooth or glossy’): probably from Old English and related to Old Norse slíkr ‘smooth’; compare with sleek.

wiktionary

ref

From the adjective slick.

From slick(“to smooth or make slick”) +‎ -er.

etymonline

ref

slicker (n.)

1851, "tool for smoothing leather," from slick (v.). Meaning "waterproof raincoat" is from 1884; sense of "clever and crafty person" is from 1900.