What does "it's not over till the fat lady sings" mean?
When operas are performed it is customary fir the show to end with a robust female singing the last ballad. So they make up the idiom or saying from that.
It is idiom.
Like revenge! Like someone isn't done until they get back at the other person!! Because the other person probly did something to them!
The saying means that we should not presume the outcome until everything is over. It is like saying "it ain't over untill it's over". This was first used by commentators of a sports event.