A blow for a blow; an ill deed for an ill deed. The phrase “tit for tat”, which expresses a moderate retaliation, goes back only about four centuries in its present form, but before that it was “a tip for a tap,” which goes back certainly a hundred years earlier and probably much more than that.
A “tip,” in Middle English, was a light blow; a “tap,” then as now, was also a light blow. So the expression is far weaker than the old Hebrew adage, “an eye for an eye, and a tooth for a tooth.”
We use it chiefly in reference to speech: an insult for an insult; an unkind remark in return for an unkind remark.
Probably the original expression was influenced by the French phrase, “tant pour tint”, literally, so much for so much.
