I love this question. Fob and dongle. (For some reason those words remind me of Miller's Crossing, though i'm probably thinking of fop and dangle.) A fob is, of course, that plastic thing on your keys that locks/unlocks your doors and more. A dongle is that thing that Autodesk makes you hang off the back of your PC to run Autocad or Maya.
As words, fob has been around for centuries while dongle is a more recently made-up word to describe a hardware key. Fob is interesting in that it meant a small pocket, while now we put fobs in pockets with our keys. You can also have a keyring with a fob and a dongle on it, the former to open your car and the latter to open Maya.
Definitions and Links
fob (from Online Etymology Dictionary) n. 1653, "small pocket for valuables," probably related to Low Ger. fobke "pocket," High Ger. fuppe "pocket." Meaning "chain attached to a watch carried in the fob" is from 1885.
v. "to cheat," 1583, from obsolete noun fobbe "cheat, trickster" (1393), perhaps from O.Fr. forbe "cheat." Alternative etymology holds that the word is perhaps related to Ger. foppen "to jeer at, make a fool of" (see fop); or from Ger. fuppen, einfuppen to pocket stealthily, which would connect it to fob (n.). To fob (someone) off is first recorded 1597.
fob off (from Yahoo Education) v. To dispose of (goods) by fraud or deception; palm off: fobbed off the zircon as a diamond.
dongle (from Wordnik) n. noun A hardware device that serves as copy protection for certain software by rendering the software inoperable when the device is not plugged into a printer port.