A jiffy is an actual measurement of time.
You’ve probably heard people say things like “I’ll be there in a jiffy,” using “jiffy” to mean a very short period of time — something like the blink of an eye. But it may surprise you to learn that for some scientists, the term has a more precise definition. That definition varies depending on who’s doing the talking: The physical chemist Gilbert Newton Lewis (1875–1946) defined a jiffy as the length of time it takes for light to travel 1 centimeter in a vacuum. However, some physicists have defined a jiffy as the time it takes light to travel 1 femtometer — one-millionth of a millionth of a millimeter. By this account, each second contains roughly three hundred thousand billion billion jiffys.
But a jiffy has also been defined outside of physics and chemistry. An electrical engineer, for example, might describe a jiffy as the time it takes for a single cycle of alternating current, which is one-fiftieth or one-sixtieth of a second depending on the electrical system. Whatever definition holds true, one thing is certain — no one in the history of the world has ever truly accomplished much “in a jiffy.”