Pirates > Maroons
Maroons were originally a group of slaves on Jamaica that revolted against their British masters and despite constant efforts managed to hold off the royal forces and established their own culture in the hills of the island. They were a famous icon for defiance against tyranny, much like the pirates themselves. Therefore it was only natural that freed slaves who became pirates called themselves Maroons partially in homage to their brothers but also to themselves to show they were not just relegated to the position of being a slave.
In fact, piracy was one of the best economic opportunities that African males would have for nearly two hundred years and in the work place they were treated as one of the crew. Given all of the rights and benefits conferred upon his British, French, Dutch or European counterpart the freed slaves were entitled to their share of the loot and healthcare if they were injured. The social interactions between pirates and slaves.
Pirates would often liberate slaves from ships they captured in order to bolster their crew. The slaves were eager to join for the aforementioned economic reasons and the fact they would not have to be slaves anymore. Plus getting the chance to jump over to a European merchant ship during a boarding and slice up some of their former captors was a bonus all in itself. Many pirates such as Bartholomew Roberts and Edward 'Blackbeard' Teach were known to have had many freed slaves aboard their pirate crews.