jmh, great article. thankyou. it suggests that this was a situation WAITING for an expression i.e. wait for the end. but the opera connection is dismissed too soon, i think. there are operas where the heroine does sing a big aria at the end, purcell's "dido and anaeas" is one. in tosca she does sing, but not exactly an aria, but puccini was not a conventional aria/recitative man. in many operas the heroine dies before the end of the opera, like othello, and she can sing a hugely lengthy aria while dying. this is just asking for someone to make fun of it. and compare "it's not over till the fat lady sings" with "it's not over till the short tenor in platform shoes sings" for colour.
but what is the church connection? could someone enlighten me as to what service concluded with a fat lady singing?
and with bill clinton and andre agassi chipping in could it be this expression is gaining popularity when it's exactly the wrong era to be referring to "fat ladies" at all?