subs. (common).A generic reproach: spec. a rough, brutal, uncouth character. In America = a back-country lout, a greenhorn (BARTLETT). [A name given by Swift in his Gullivers Travels (1726) to a race of brutes, described as having human forms and vicious and degraded propensities. They were subject to the Houyhnhnms, or horses endowed with human reason.] As adj. = boorish, loutish, uncouth.
1772. R. GRAVES, The Spiritual Quixote, IV. x. To see a noble creature start and tremble at the passionate exclamation of a mere YAHOO of a stable-boy equally excites my pity and my indignation.
d. 1790. T. WARTON, Newmarket, 170. That hated animal, a YAHOO squire.
1861. H. KINGSLEY, Ravenshoe, lv. And what sort of fellow is he? said Lord Saltire. A YAHOO, I suppose? Not at all. He is a capital fellowa perfect gentleman.
1900. R. H. SAVAGE, Brought to Bay, v. You frontier YAHOOS know nothing but herding cattle.