Green’s Dictionary of Slang

jiffy n.

also giff, giffey, giffy, jef, jeffy, jif, jiff, jiffey, jiffie, jiffin

1. [late 18C+] a moment, a very short time; almost invariably in phr. in a jiffy; occas. in a jiff; also intensified as half a jiff(y).

2. [late 19C] a very small amount.