boot-licker (n.)

"covering for the foot and lower leg," early 14c., from Old French bote "boot" (12c.), with corresponding words in Provençal, Spanish, and Medieval Latin, all of unknown origin, perhaps from a Germanic source. Originally of riding boots only.

From c. 1600 as "fixed external step of a coach." This later was extended to "low outside compartment used for stowing luggage" (1781) and hence the transferred use in Britain in reference to the storage compartment in a motor vehicle (American English uses trunk (n.1)).

Boot-black "person who shines boots and shoes" is from 1817; boot-jack "implement to hold a boot by the heel while the foot is drawn from it" is from 1793. Boot Hill, U.S. frontier slang for "cemetery" (1893, in a Texas panhandle context) probably is an allusion to dying with one's boots on. An old Dorsetshire word for "half-boots" was skilty-boots [Halliwell, Wright].

Old English liccian "to pass the tongue over the surface, lap, lick up," from Proto-Germanic *likkon (source also of Old Saxon likkon, Dutch likken, Old High German lecchon, German lecken, Gothic bi-laigon), from PIE root *leigh- "to lick."

French lécher, Italian leccare are said to be Germanic loan words. The figurative lick (one's) lips in eager anticipation is from c. 1500. Lick-ladle (1849) was an old phrase for a (human) parasite. To lick (someone or something) into shape (1610s) is in reference to the supposed ways of bears:

Beres ben brought forthe al fowle and transformyd and after that by lyckyng of the fader and the moder they ben brought in to theyr kyndely shap. ["The Pylgremage of the Sowle," 1413]