1797 T. Morton i. i. 5 Frank (without). Woyh! Whoh! Smiler.
1809 R. Kerr 503 Formerly, in speaking to their horses, carters..in calling to stop used the incommunicable sound of prroo, now wo, or woy.
1828 W. Carr (ed. 2) Who, Woy, a word used to stop horses in a team.