old timer (1872)

“They [the Brooklyn Atlantics] were compelled to call on Mr. Galvin, one of the old Timers, to play second base, and as Mr. Galvin has not had much practice for several years it could not be expected that he would do very well at first ….” “Details of the Great Victory of the Boston Nine Over the Atlantics,” Boston Herald, May 8, 1872, p4

NOTE: John Galvin had played with the Brooklyn Atlantics from 1863 to 1867

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1905.  (The Sporting Life, Oct. 7, p.21; Edward J. Nichols).