In its most primitive form, the trope is a No, You variant of the Lame Comeback, but with 'your mom' substituted for 'you' (' Your mom's a lame comeback!') The next step up is ' That's what your mom said!', becoming a more explicit Double Entendre. After all, Even Bad Men Love Their Mamas, and going directly after their mother is a surefire way to strike a nerve in one's opponent. In a war of Volleying Insults, insulting the opponent's mother is a useful snappy comeback. Your mom's so stupid, when she was asked to Describe Your Mom Here, she said she didn't know your mom.
