Do you sometimes anticipate an occasion so highly that you act on it before it is time? Maybe you interrupt someone while they’re speaking or go ahead and book your friend a movie ticket before they’ve confirmed they’re coming. This is what’s colloquially called ‘jumping the gun’ and here’s how this particular idiom originated.
It’s fairly straightforward. Basically, from as early as the 20th century, ‘jump the gun’ (or ‘beat the gun’) was used in relation to competitors in track and field races who were in such a state of expectation before the race that they leapt into action before the starting pistol was fired.
One early reference comes from Crowther and Ruhl’s 1905 text Rowing and Track Athletics:
“False starts were rarely penalised, the pistol generally followed immediately on the signal ‘Get set!’ and so shiftless were the starters and officials that ‘beating the pistol’ was one of the tricks which less sportsmanlike runners constantly practised.”
The earliest citation of ‘jump the gun’ isn’t related directly to athletics but is used in a manner that most closely reflects how we use the phrase today. It can be found in the newspaper The Iowa Homestead from November 1921:
“Give the pigs a good start; jump the gun, so to speak, and get them on a grain ration before weaning time.”
In both examples, the phrase was used to describe a sudden or unexpected movement. Other, earlier phrases to parallel this one are ‘jump someone’s claim’, ‘jump ship’ and the more contemporary ‘jump the queue’.