In a long look at the history of tattoos, Hunter Oatman-Stanford details their naval origins:

Body art was particularly well-suited to the transient and dangerous nature of life at sea. "These sailors were traveling the world, and wanted to bring back souvenirs from places they had visited," explains [Tattoo Archive founder C.W.] Eldridge. "Aboard a ship, you don’t have much room to carry fancy souvenirs, so you end up getting tattoos as travel marks." By the late 18th century, navy records show that around a third of British and a fifth of American sailors had at least one tattoo, while other accounts reveal that French, German, and Scandinavian navies were also fond of getting inked.

(Hat tip: Neatorama. Photo: Tattooed sailor aboard the USS New Jersey, December 1944. By Lt. Comdr. Charles Fenno Jacobs from Wikimedia Commons)