Yours, Etc.: Origins and Uses of 8 Sign-Offs
mid-15c., from jaw (n.) + bone (n.). Hence jawboning "lecturing, hectoring," a term associated with the U.S. Lyndon Johnson presidential administration (1966); cf. jaw (v.).
jawbone jaw·bone (jô'bōn')n. The maxilla or, especially, the mandible.
Credit or trust, esp financial: Try as he might he got no jawbone from the bankers (1862+)