Pan (Home Plate) (1888)

“Game was called at 2:30, with the Portlands at the bat. … Then Bentle came to the pan.” Morning Oregonian (Portland, OR) July 02, 1888; pg. 3. [Joel S. Berson]

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1891. “These three men make the pitchers put them over the pan day in and day out” (Sporting Times, May 23; David Shulman).