An idiom, developed in the late 1800's, that nowadays is used in the literal sense: that the person saying this, is telling the person receiving that their mother, is in fact a
homosexual, or merely as an insult, that makes no literal sense. But in its half century (or so) of use was in the actual sense of an idiom; in that it could be used in a slightly more nonlinear sense.
My analysis of the idiom:
I first like to look at the use of the work "you're" which is the contraction of the words "you are," which I can believe is a way to really emphasize how personal the use of the phrase can be. Then there's the word "mom,"
the person who birthed you, the reason that you're currently on this world. Now many people are upset whenever you talk about their mother in a
negative sense, and since this is right before the word "gay," whose definition relates to being attracted to the same sex which is taboo in culture today, and was much more in previous centuries, many believe this to have a negative connotation while in conjunction with the word "mom." But I find it to have been used in a much lighter sense in previous centuries, not being used as an insult, but more a compliment generally meaning "your mother is quite
lighthearted," since gay isn't just a way as classifying someone as being attracted to the same sex, but also as an adjective to describe a good experience, or a nice person.
