In WoW, Pirate's Day do be the Azerothian equivalent, with the Dread Captain DeMeza, the Scourge o' the South Seas, invadin' Booty Bay fer one day only. Players can speak t' her t' be transformed into a Dread Corsair and temporarily join the crew for the one related holiday achievement. John and Mark do be present as secondary characters under their respective nicknames: Ol' Chumbucket and Cap'n Slappy. Captain DeMeza do be most likely a reference to the Dread Pirate Roberts from The Princess Bride, although thar be very little information about her.
Here be the section about Linguistic Background from the TLAPD wikipedia entry:
Actor Robert Newton, who specialized in portraying pirates, especially Long John Silver in the 1950 Disney film Treasure Island, and in the 1954 Australian film Long John Silver, and as the title character in the 1952 film Blackbeard, the Pirate, is described as the "patron saint" of Talk Like A Pirate Day. Newton was born in Dorset and educated in Cornwall, and it was his native West Country dialect, which he used in his portrayal of Long John Silver and Blackbeard, that some contend is the origin of the standard "pirate accent".
Keep in mind that there do be many a swashbuckler lookin' fer PVP on the high seas. T' talk to the Dread Captain, assign a keybind t' yer Interact With Target command. That way, ye can salute the captain without firin yer cannons at another player. Arrrr!
The archetypal pirate grunt "Arrr!" (alternatively "Rrrr!" or "Yarrr!") first appeared in fiction as early as 1934 in the film Treasure Island starring Lionel Barrymore, and was used by a character in the 1940 novel Adam Penfeather, Buccaneer by Jeffrey Farnol. However it was popularized and widely remembered with Robert Newton's usage in the classic 1950 Disney film Treasure Island. It has been speculated that the rolling "rrr" has been associated with pirates because of the location of major ports in the West Country of England, drawing labor from the surrounding countryside. West Country speech in general, and Cornish speech in particular, may have been a major influence on a generalized British nautical speech. This can be seen in the Gilbert and Sullivan operetta The Pirates of Penzance, which is set in Cornwall; although the play did not (originally) use the phrase "arrr", the pirates used words with a lot of rrr's such as "Hurrah" and "pour the pirate sherry".