bootlick. (verb) To gain favor by flattery, fawning, or obsequious behavior.

Dogs are notoriously obsequious, as is repeatedly stated throughout these entries. They are constantly seeking favor and social recognition. Dogs are also notorious lickers, and often known for licking less than luscious items, so we are not much surprised to find boots among them. Boot licking as a description seems to have fallen out of favor: perhaps this is because the licking of boots is increasingly associated with foot fetishes and bondage and discipline fantasies.

Webb Garrison offers this colorful origin, “Returning from a day in the woods, hunters often had bloody boots. Hungry curs, running up to them, would fight over the privilege of licking off the blood.”