<P>... months of imprisonment in the bull - pen, a structure unfit to house cattle, enclosed in a high barbed - wire fence . </P> <P> Penned up in bullpens as a response to violence, many hundreds of union men had been imprisoned without trial . Peter Carlson wrote in his book Roughneck, </P> <P> Haywood traveled to the town of Mullan, where he met a man who had escaped from the bullpen . The makeshift prison was an old grain warehouse that reeked of excrement and crawled with vermin . Overcrowding was so severe that some two hundred prisoners had been removed from the warehouse and quartered in railroad boxcars . </P> <Ul> <Li> In the 1800s, jails and holding cells were nicknamed "bullpens", in respect of many police officers' bullish features--strength and a short temper . </Li> <Li> 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 . </Li> <Li> The name may be a reference to rodeo bulls being held in a pen before being released into the main arena . </Li> <Li> Latecomers to ball games in the late 19th century were cordoned off into standing - room 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 . </Li> <Li> At the turn of the century, outfield fences were often adorned with advertisements for the Bull Durham brand of tobacco . Since relievers warmed up in a nearby pen, the term "bullpen" came about . </Li> <Li> Manager 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 would not be a bother to the rest of the team--the bullpen . How serious he was when he made this claim is not clear . </Li> <Li> Jon Miller, a baseball play - by - play announcer with ESPN television, said the term is derived from the late 19th century . The New York Giants first played at the Polo Grounds, which opened around 1880 . The relief pitchers warmed up beyond the left - field fence, and in the same area was a stockyard or pen that had bulls in it . </Li> <Li> In 1913, an Ohio veteran of the Civil War contrasted a current baseball game with "a good game uv old time bull pen, the way us boys uster play it ." This suggests that bullpen was the name of a game . </Li> </Ul>

Where does the term bull pen come from