the.com/key fob

means A small wireless remote attached to your keys that locks, unlocks, and sometimes starts your car, broadcasting a short-range radio signal when you press it.

from 'Fob' has been English since the 1600s for a small pocket or pendant attached to a watch chain — a little dangling thing you could reach for quickly. When electronic key transmitters appeared in the late 20th century, they inherited the name because they hung off a keyring the same way old watch fobs hung off a chain: a small appendage riding along with something more important, until it quietly became the part you actually use.