What's in a name? MLB.com
 

Interesting article on origin of bb team names.

http://m.mlb.com/cutfour/2016/01/14/...mlb-team-names

The story of the Pirates name is wrong, though it does include some facts. He makes it sound like the Innocents nickname had something to do with the Bierbauer incident, which happened after the 1890 season was over. I've read local newspapers from the entire 1890 season(about 90% is available) and I never saw the Innocents name in print.

The team also never renamed themselves the Pirates in 1891, that was something done by newspapers in a few of the towns they visited such as Philadelphia, Cincinnati and Boston. You would see Pirates mentioned in the Pittsburgh newspapers during those games, but only if they were recaps from road game sent to the paper. The local press didn't follow the team everywhere.

The "Pirates" name didn't fully go into use until the end of Spring Training in 1895 and even then the team's actual name was "The Pittsburg Base Ball Club" with no H on the end of the city name because they didn't spell it that way back then.

In 1891 they were called the Allies, Pittsburgs or Alleghenys by the local press
In 1892 they were called the Hanlon's after manager Ned Hanlon. When he left, they became known as the Pets because manager Bill McGunnigle ran the practices with a whistle, so they said they were his pets.
In 1893 it went back to Pittsburgs/Allies/Alleghenys
In 1894, they were known as the Braves more often than not for the entire season.
In 1895, they decided on Pirates at the end of Spring Training and it stuck.

It should also be pointed out that at that time they were owned by William Kerr, who went by Captain Kerr and had a huge, unruly parrot in his office sitting just over his shoulder, so you could speculate that someone named "Captain" who has a parrot just over his shoulder all the time might conjure up the name Pirates himself.