The baseball bullpen dates back more than 100 years. The term comes from an unlikely source: advertising.
In many ballparks in the early 20th century, advertisements were printed on the walls in many places. In many parks, ads for tobacco that featured a “bull” were on the outfield walls nearby the spare pitching mounds used by relief pitchers.
Gradually, “reserve” or “relief” pitchers sat on benches near the pitching mounds, and when these “bull” themed ads became popular, observers adopted the name “bullpen.”
The term bullpen has been used to describe the place where relief pitchers are located even though there are few bull-ads on those walls these days.
