From Wiktionary, the free dictionary
quite so
- indeed; I agree with that
1898, Kate Douglas Wiggin, chapter 7, in Penelope’s Progress […], Boston, Mass., New York, N.Y.: Houghton, Mifflin and Company […], →OCLC:" […] He asked if it were really true that they ate chalk and slate pencils. Wasn't that unendurable? I answered that those were the chief solid articles of food, but that after their complexions were established, so to speak, their parents often allowed them pickles and native claret to vary the diet."
"What did he say to that?" I asked.
"Oh, he said, 'Quite so, quite so;' that was his invariable response to all my witticisms.
