fob 1 
(fŏb)
(fŏb)n.
1. A small pocket at the front waistline of a pair of trousers or in the front of a vest, used especially to hold a watch.
2.
a. A short chain or ribbon attached to a pocket watch and worn hanging in front of the vest or waist.
b. An ornament or seal attached to such a chain or ribbon.
3. A key fob.
[Probably akin to Low German Fobke, small pocket.]