Everybody who familiarizes themselves with the art of typing likely discovers that there are words that they seldom type, or that are more difficult than others for no conceivable reason other than unfamiliarity. It's not even the problem with being unfamiliar with a word, such as "quizzical," "equilibrium" or "zygomorphic," it's muscle memory formed by practiced usage of the keyboard at fault. Unless you regularly type quite a lot with your left pinky, of course; that would probably help.