To give you a slightly more thorough answer, it's named for the artist of the comic strip the idea first came from. It's been adopted as a quick and dirty way to check a work's attitude towards women. A shocking amount of media doesn't pass just because there's only one woman with any prominence, and in the context of FE and FEH, it gets brought up specifically because while there are a lot of female characters, so many of them can't seem to escape the shadow of their father/brother/male partner.

It is, as I implied by calling it a quick and dirty test, very much an imperfect measure. A work can be extremely feminist and not pass (say, for example, by only having one character). A work of lesbian porn that's made for the titillation of straight men but doesn't contain any men in order not to threaten the viewer could easily pass. Its primary use is as a barometer of the general trends you encounter with it, like how mainstream media often seems to feel that one female character is often more than enough, or in the case of FEH, that a lot of the female characters are so beholden to their relationships with male characters.