From the essay bearing the same name by
Mark Twain. The essay was published in 1923, after Twain's death, but is thought to have been written in 1901.
A corn-pone opinion is an opinion that is not an original opinion--"an opinion which is coldly reasoned out in a man's head, by a searching analysis of the facts involved, with the heart unconsulted, and the jury room closed against outside influences"--but is rather, an opinion borne of association with and sympathy for a belief or cause, not reasoning and examination; that "hardly a man in the world has an opinion on morals, politics, or religion which he got otherwise than through his associations and sympathies".
Twain writes that when he was a boy, he befriended a slave, "who daily preached sermons from the top of his master's woodpile, with me for the sole audience", and that the idea came from one of the "sermons" and impressed upon him deeply.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."