What was the original English subtitle of Assassin's Creed IV?

The original English subtitle of Assassin's Creed IV is Black Flag.

Released in 2013, Assassin's Creed IV: Black Flag follows Edward Kenway, a Welsh privateer who becomes entangled with the Assassins during the early eighteenth-century Golden Age of Piracy. The game is set mainly in the Caribbean.

Edward commands the ship Jackdaw, and naval exploration is one of the game’s defining features. Players can raid vessels, upgrade the ship, hunt animals, explore islands, and visit ports such as Havana, Nassau, and Kingston.

Black Flag is sometimes described only as a pirate game, but its story remains tied to the Assassin-Templar conflict and to the series’ modern-day narrative. Edward is also the grandfather of Ratonhnhaké:ton, known as Connor, the protagonist of Assassin's Creed III.