fob (n.)youdaoicibaDictYouDict[fob 词源字典]
1650s, "men's small waist pocket for valuables," of uncertain origin, probably related to Low German fobke "pocket," High German fuppe "pocket," "a dialectal word used in Livonia" [Klein]. Meaning "chain or ornament attached to a watch carried in the fob" is by 1888, shortened from fob chain.[fob etymology, fob origin, 英语词源]
fob (v.)youdaoicibaDictYouDict
"to cheat," late 14c., from obsolete noun fobbe "cheat, trickster" (late 14c.), which perhaps is from Old French forbeter "to deceive, trick, dupe." Alternative etymology holds that the word is perhaps related to German foppen "to jeer at, make a fool of" (see fop); or from German fuppen, einfuppen "to pocket stealthily," which would connect it to fob (n.).

Meaning "to put or shift off (something) by pretense" is from 1650s; to fob (someone) off "put him off deceitfully" is from 1590s. Related: Fobbed; fobbing.