"fold of flesh under the jaw," 1590s, alteration of Middle English cholle "fold of flesh hanging from the jaw" (c.1300), perhaps from Old English ceole "throat," from PIE *gwele- "to swallow" (see glut). This word and jowl (n.1) influenced one another in form and sense.
"jaw," 1570s, alteration of Middle English chawl (late 14c.), chavel (early 14c.), from Old English ceafl, from Proto-Germanic *kefalaz (cf. Middle High German kiver, German kiefer, Old Norse kjoptr "jaw," Danish kæft, Flemish kavel, Dutch kevel "gum"), from PIE *gep(h)- "jaw, mouth" (cf. Old Irish gop, Irish gob "beak, mouth"). The change from ch- to j- has not been explained.