What’s the origin of "tit for tat"?

Dear Cecil:

What is the origin of "tit for tat"? What is tat? And where can I get some in order to get the former?

Cecil replies:

Cecil replies:

You’re a stitch, PK. "Tit for tat" is a corruption of "tip for tap," blow for blow, which first turned up in the 15th century. (That’s "tip" as in foul tip, a light or glancing shot.) I was thinking I could work in a joke here about "boobs," but it’s just not happening, which is probably lucky for both of us. Go thou and pun no more.

Send questions to Cecil via cecil@straightdope.com.

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