E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
properly means to stand front to front. In savage nations opposing armies draw up front to front before they begin hostilities, and by grimaces, sounds, words, and all conceivable means, try to provoke and terrify their vis-à-vis. When this affronting is over, the adversaries rush against each other, and the fight begins in earnest.
Affront. A salute; a coming in front of another to salute.
Only, sir, this I must caution you of, in your affront, or salute, never to move your hat.Green: Tu Quoque, vii. 95.