“Kelly got on the coaching line near first, and kept up a running fire with his own players. ‘Come on now boys, we’re out for the money; let’s give them a Garrison finish.’” Boston Globe, October 2, 1889, p3
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1896. “With the score 5 to 1 against them, the colts [sic] started in for a ‘garrison finish’ and batted out a victory” (The Boston Globe, July 23; Peter Morris).