See quotation.
1857. NO SIR-REE had a pretty long run, and is not out of date quite yet. But one of the quaintest, quietest, most musical, and most engaging forms of acquiescence is in the new and popular phrase of ‘That’s so,’ which is working its way into common parlance.—Knick. Mag., xlix. 86 (Jan.). (Italics in the original.)
[See the A.V. of Acts vii. 1. “Are these things so?”]
