“Hell bent for leather” appears to be a combination of two other phrases: “hell bent” and “hell for leather”. “Hell bent" first appears in American usage about 1825 and inferred that the rate of speed was such that a rider and horse were flirting with or headed for ("bent on") disaster. Charles Earle Funk, in "
A Hog on Ice," (1948) says that "hell for leather" is a British expression, apparently originating in the British army in India. Possibly Rudyard Kipling coined it, and he was certainly the first to record it, although he may just have been quoting common army slang. His first usage is in "
The Story of the Gadsbys" (1889), ”Here, Gaddy, take the note to Bingle and ride hell-for-leather”. 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. It remains unknown as to when the two expressions, one American and one British, came into combined use. (With thanks to phrases.org and word-detective.org.)
