“….the game was perfectly played by the Hartfords, the only error being a wild pitch by Cummings.” Hartford Courant, April 25, 1875, p2
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1904. “[Otto] Hess wild-pitched [Boileryard] Clarke to second” (The Washington Post, Aug. 25; Peter Morris).