1
general::
Also, lick one's lips. Anticipate with great pleasure. For example, The kids were licking their chops as Mother described the family vacation plans, or I couldn't help but lick my lips when she talked about the menu. Both expressions allude to anticipating a tasty morsel of food. The second is the older, dating from about 1500 and used interchangeably with lick one's fingers, now seldom heard. The first Also served as 1930s jazz slang for warming up, chops meaning "the jaw or mouth" (a usage dating from the 1300s).
American Heritage Idioms