“Detroit made the first run on singles by Richardson and Brouthers, a passed ball and Thompson’s sacrifice bunt.” The Boston Globe, August 14, 1887, p2
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1935. “A sacrifice bunt is a bunted ball laid down for a like purpose” (Ralph H. Barbour, How to Play Better Baseball, p. 173; David Shulman).