The word jiffy has held many different meanings throughout history. Most people don't even realize that it's a unit of measurement, and use it interchangeably as moment; however, it does have scientific meaning as well. Nowadays, it's referred to by computer animators as the time it takes to go from one frame to another, or 0.1 seconds conventionally. Prior to that, it was used by engineers to denote the time between electrical alternating currents, which could either be 0.0167 or 0.02 seconds. It's also been used to refer to much smaller times, such as the time for light to travel one centimeter (0.0000000000334 seconds) or the time for light to travel one Planck length (it has 43 zeroes in front of it). But before these "official" defined usages, "jiffy" has been used colloquially for a while. It was first attested in 1785 and in early days was thought to be the time for a lightning strike to occur, possibly having came from a code word used by eighteenth-century hustlers to mean "lightening".
Adam Aleksic, a leading contender for valedictorian of his high school, is a 208-month-old boy with disturbing interests in etymology, vexillology, geography, and law. Adam would like to one day visit Tajikistan and just won an essay contest on linguistics!
The Etymology Nerd