Where does the word “Chopfallen” come from and What does Chopfallen mean?

“To lick one’s chops,” usually interpreted as indicating supreme pleasure, such as that from lapping the last taste of gravy or the last crumb of cake from one’s jaws, not only shows us the meaning of chop in the term chopfallen, but also pictures the exact opposite, the antonym, of the whole term.

One who is chopfallen has been made supremely unhappy; he has had the ground knocked out from beneath him; he is crestfallen; he has a hangdog appearance, or, in brief, he has been so taken aback, so discomfited, that his chop, or jaw, has fallen open.