jaw (n.) Look up jaw at Dictionary.com
late 14c., "the bones of the mouth," perhaps from Old French joue "cheek," from Gaulish *gauta "cheek," or perhaps a variant of Germanic words related to chew (q.v.); compare also jowl. Replaced Old English ceace, ceafl.
jaw (v.) Look up jaw at Dictionary.com
1610s, "to catch in the jaws, devour," from jaw (n.). In slang from 1748, "to gossip, to speak" 1810, "to scold." Related: Jawed; jawing. Hence 19c. U.S. slang jawsmith "talkative person" (1887).