The definition of “all but” means “very nearly,” but this makes no sense logically. For instance, if someone says “That word is all but forgotten” it means that whatever word the speaker is referring to is almost forgotten. But if you take apart the phrasing you’ll see that it means almost the exact opposite. By saying that something is all but forgotten, one is really saying that the thing is everything but forgotten i.e. it may be other things, but it is very much remembered. How is it that “all but” came to mean “very nearly” when really all should be negated by but, and that which comes after but should be in the affirmative?
(I understand that this may be worded in a slightly...abstruse manner. I apologize if this is the case. Perhaps someone can word it better?)