The first written reference to such songs emerged in the mid-16th century. The term "sea shanty" as a naval work song did not develop until the early 19th century, where they were used aboard American merchant vessels. About Assassin's Creed Sea Shanties Sea shanties are work songs commonly sung aboard ships by sailors either to keep the crew in time while performing tasks or just for entertainment.
The use of the term "sea shanties" in Assassin's Creed IV: Black Flag and Assassin's Creed: Rogue is anachronistic.