The term "armchair" is sometimes used to describe a hobbyist or non-expert enthusiast, e.g. "armchair psychologist." It seems to make a certain kind of sense, because we can imagine people offering their opinions about their pet subjects from the comfort of their own armchairs without having to, like, actually get up and study or do anything practical.

It just occurred to me though that this is an unusually belabored metaphor, requiring a lot more mental gymnastics to explain than most metaphors that have caught on to the extent it has.

Is it possible that "armchair" is not a metaphor, but a Mondegreen for "amateur"? I don't think I ever noticed until just a few minutes ago how similar the two words sound.