Q From Peter Rugg: Where did tit for tat come from?
A It’s the littlest words that often give us the most trouble in sorting out their origins. They’re likely to be the ones that have proved to be the most mutable in the spoken language. This curious phrase is a classic example.
In the sixteenth century, it was tip for tat. Another form, used by Shakespeare and almost certainly from fencing, was tap for tap, which makes plain the underlying idea of a reprisal or retaliation that’s roughly proportionate to its cause.
Tat in tit for tat isn’t a distinct word at all but an instance of a type of reduplication in which the internal vowel changes from i to a, as in chit-chat, flimflam and knick-knack. Tip here is the same as tap, a light blow. Tit is not in the mammary sense but comes from an old verb that likewise could mean to strike a light blow.
All these words have an idea of smallness about them: a tit can also be a small bird (originally titmouse but it was the tit part that communicated small size, since mouse isn’t the rodent but a version of mose, an Old English name for the same bird); at one time tit could be a small or part-grown horse or a girl or young woman. Tip can also be an extremity or small point. The ultimate origins of most of these are uncertain but some may be imitative.
After all that, you will understand that we must dismiss the common belief that tit for tat is a corruption of this for that.
I am suspicious of two other statements about its origin which appear in some reference works. It has been suggested that it’s related to the French tant pour tant, which chefs will know as a mixture of equal parts of fine sugar and ground almonds. It seems to have once meant “like for like” and is ancient enough that a bashed-about version is in Love’s Labour’s Lost: “So pertaunt-like would I o’ersway his state”. But if it was ever common it is improbable as the source of tit for tat, as the links to the other short English words I’ve listed are too strong.
Most works that mention that source also suggest that it could be from a Dutch phrase, dit vor dat, in the same sense, though my Dutch contacts say it doesn’t exist in the language today nor in old texts. I suspect uncritical borrowing of erroneous material from earlier sources, the curse of third-rate reference books.