Where did the term the 'bullpen' originate?
The origin of the term bullpen is debated with no one theory
gaining unanimous, or even substantial, prevalence over another.
The term first appeared in wide use shortly after the turn of the
20th century and has been used since in roughly its present
meaning. Some of the most common theories are: The bullpen
symbolically represents the fenced in area of a bull's pen, where
bulls wait before being sent off to the slaughter. The relief
pitchers are the bulls and the bullpen represents their pen. Late
arrivers to ball games in the late 19th century were cordoned off
into standing room only areas in foul territory. Because the fans
were herded like cattle, this area became known as the bullpen, a
designation which was later transferred over to the relief pitchers
who warmed up there. At the turn of the century, outfield fences
were often adorned with advertisements for Bull Durham Tobacco.
Since relievers warmed up in a nearby pen, the term bullpen was
created. In the 1800s, jails and holding cells were nicknamed
bullpens, in respect of many police officers' bullish features --
strength and a short temper. The term was later applied to bullpens
in baseball. Casey Stengel suggested the term might have been
derived from managers getting tired of their relief pitchers
"shooting the bull" in the dugout and were therefore sent
elsewhere, where they wouldn't be a bother to the rest of the team
-- the bullpen. How serious he was when he made this claim is not