What does the expression “hell for leather” mean and Where did it come from?

In America we’d say, “in a hell of a hurry,” with the same meaning; but this is a British expression, apparently originating in the British army in India.

Possibly Kipling coined it, for he was the first to record it, though he may have been actually quoting army speech.

His first usage is in The Story of the Gadsbys, in that portion of the story (“The Valley of the Shadow”) where Mrs. Gadsby is just emerging from “the Valley.”

His second use of the expression is in Mulvaney’s episode with “My Lord the Elephant,” in Many Inventions.

Though the term must originally have referred to the terrific beating inflicted upon leather saddles by heavy troopers at full speed, even by Kipling’s time it had acquired a figurative sense indicating great speed, on foot, by vehicle, or by horse.