arr · noun, noun1
By abbreviation.
arr · interjection, verb2
Possibly from aye. The pirate-imitation form was derived from the West Country dialect after its use by West Country-born actor Robert Newton (1905–1956) in the films Treasure Island (1950) and Blackbeard the Pirate (1952)—and the former’s spin-off media—in which he played, respectively, the fictional pirate Long John Silver and the historical pirate Edward “Blackbeard” Teach (c. 1680 – 1718; also a West Country native).
Etymology from Wiktionary, CC BY-SA 4.0.