See quotation, 1827.
1827. When the Yankee says pretty, he does not mean handsome but agreeable; and when he says ugly, he does not mean ill-looking, but vicious. Thus he will say of a horse, He is a very handsome horse, but he is as ugly as Satan.Mass. Spy, Nov. 28: from the Berkshire American.
1878. A half-breed squaw, about as pretty as a wild-cat struck with a club.J. H. Beadle, Western Wilds, p. 387.