Origin of: "I don't chew my cabbage twice."

It is probably the combination of two sayings as suggested by the Phrase Finder:

I don't chew my cabbage twice - Response when someone asks you to repeat what you just said. This phrase is probably a combination of: I don't chew my baccer (tobacco) twice and I don't boil my cabbage twice.

I don't boil my cabbage twice. 1888. "In the country, especially in the country towns of Pennsylvania, this is a very common expression, generally pronounced, 'I don't bile my cabbage twict.' It signifies that the person uttering it does not intend to repeat an observation." "Dictionary of American Regional English," Volume 1 by Frederic G. Cassidy (1985, Belknap Press of Harvard University Press, Cambridge, Mass., and London, England, Page 609).

"I don't chew my cabbage twice" is one of many descendants of the Ancient Greek proverb "dis krambe thanatos" ("cabbage twice over is death," meaning repetition is tedious). An early use of this idea is seen in the Roman satirist Juvenal where (7.155) he writes, "occidit miseros crambe repetita magistros" (cabbage twice over kills the poor professors).