In like Flynn
Firstly, the expression is not in like flint, which is often heard. It is in like Flynn and means to be committed to the hilt. It is first cited from the mid-1940s. The 1967 movie In Like Flint starring James Coburn was simply a spoof on the original expression. Unfortunately, this has caused many people to use in like flint instead of the original in like Flynn. Unless one is referring to the aforementioned movie, the correct idiom is in like Flynn. There is strong evidence that the Flynn in the idiom is Errol Flynn, the famous movie star. Especially after he was acquitted of the statutory rape of a minor in February 1943. Rumours that Errol Flynn was particularly well endowed, and reports of his serial sexual conquests, were rife during the 1940s. Some etymologists claim, however, that the expression was known in America a few years before Flynn’s rape indictment and before details of his male anatomy were publicised. They maintain that in like Flynn was rhyming slang for ‘being in or committed’, in like Flynn/in. Rhyming slang, however, never really caught on in America although, of course, some British immigrants must have brought examples with them. Whoever this other ‘Flynn’ may have been, Errol proved to almost everyone that fame (and size) really do matter. David Niven, who was a close friend of Flynn and shared bachelor premises and many debauched escapades, once said that he could never quite match up to Flynn. One still wonders what he meant exactly.