Tit for tat

If you hit me, I’ll hit you back; tit for tat.

Tit for tat is the policy of cooperating on the first move and then doing whatever the other player did on the previous move. This policy means that tit for tat will defect once after each defection of the other player.

Could it but for a longer Space / Lengthen the Bliſs it let's us taſte, / Who would not doat on't? But alas! / The Joy's too exquiſite to laſt. / Two white Herculean Pillars prop / The tufted Gin, the tempting Snare; / When they divide, then in we pop, / Before we well know where we are. / Then that for this, and tit for tat; / But when the pleaſing Minute's flown, / As uſeleſs it returns the Bait, / And both look fooliſh when 'tis done.

This is but Tit for Tat, young Gentleman. Your Father wanted to get my Eſtate from me; and I have got the Wife he intended for you. All's fair, Sir.

"You'll never get her over like that. You must coax her." / "Coax the devil. Do you think I'm going to be beat by a horse?" / "It would only be tit for tat; you beat her, so she has a right to beat you."

YVETTE. I have no idea what to make Monsieur for dinner. / FOLLBRAGUET. (beside himself) Well, that's no skin off my ass, damn it! / YVETTE. (snippily, giving him tit for tat) Well, it's certainly no skin off mine, Monsieur!

As part of the planning for a new initiative on Cuba, the NSC [National Security Council] also revived the concept of "calibrated response." A new staffer was tasked to develop a list of "tit-for-tats" with Cuba—which sanctions might be lifted or softened in response to clear steps toward democracy by the [Fidel] Castro regime.

China Warns of ‘Tit for Tat’ on iPhone Sales if Trump Starts Trade War

Fred came from Cheapside in London – an official Cockney, born within earshot of the bells of St. Mary-le-Bow – and he taught her Cockney rhyming slang. She loved its lighthearted logic: the last word in a common phrase rhymed with the word it was to replace. So "tit for tat" was "hat", and "trouble and strife" was "wife". But the best part was that you usually dropped the rhyming words and used only the first words, so "your wife's hat" became "your trouble's titfer".

Tit for tat hat / The phrase ‘tit for tat’ […] emerged as a rhyme for ‘hat’ in the late nineteenth century and was subsequently condensed to ‘titfer’ around 1930, in which form it enjoyed unparalleled success at a time when virtually everyone wore a hat.