http://en.wikipedia.org/wiki/Dead_Rabbits
The Dead Rabbits were a gang in New York City in the 1850s, and originally were a part of the Roach Guards. The name has a second meaning rooted in Irish American vernacular of NYC in 1857. The word “Rabbit” is the phonetic corruption of the Irish word raibead, meaning “man to be feared”. “Dead” was a slang intensifier meaning “very”. Thus, a “Dead Raibead” means a man to be greatly feared.
I love finding historical ephemera like this. These guys were infamous enough to have a song written about them by a hitmaker of the era, but short of some poor cinematic history by Martin Scorcese, they are completely forgotten now. Where is your badassery now, Rabbits?