The expression “to say uncle” means: To eat crow; throw in the towel or the sponge; cry quits; yield; submit.
When I was a boy, one “hollered ‘cavy'” when he was licked, but we would have been the most astonished boys in the world had anyone told us we were talking Latin.
That is, “cavy,” as I learned much later, is a corrupted contraction of peccavi, meaning, I have sinned, or, I am at fault, and this acknowledgment of guilt or fault was English usage from the sixteenth century onward.
How it came into southern Ohio, we don’t know.
And our present American expression, though arising only in this century, may also have had Latin birth.
At least, when the Roman lad was in trouble, he cried, Patrue mi patruissime, “Uncle, my best of uncles!”