to know the history of an idiom can be useful and interesting. for example, most native british english speakers know that "no room to swing a cat" means "there was not much space" and can use the idiom properly. however, few know this is because 200 years ago sailors were punished by being whipped with a "cat o' nine tails". a big space was cleared on the ship so that the person doing the whipping had room to "swing the cat".