Comes from sword fighting. It is used as a response. The first person says "En garde!" (On guard) ... and the second person says "Touché ！“ Touché means "touched", and i think it is said when the person is hit by the opponent's sword. So it means like , " You got me ! " (" You hit me! " )

touch or touche? if second - then in a word fight (when someone oppose you and you fill each other with bad words) in the beginning. Like start the fight, I'm ready.