Short for 'Fuck the Navy'. Usually written as graffiti on the walls of U.S. Navy ship's heads (i.e., restrooms, shithouses, shitters), walls around chow lines, and wooden benches. It is often believed that these statements result from job frustration and the belief that the sailors' efforts are not appreciated by the sailors' superiors, family members, or the nation as a whole. More commonly, it arises from heterosexual frustration due to the fact that there are no women to sleep with when you are on a ship (Navy is 90% male, 10% female, and most of the women get cushy shore duty billets anyway).
Petty Officer Shortshank bent down, unbuttoned his thirteen-button bell-bottom trousers (the stupidest pants in the history of pants), and repainted the toilet bowl a grim greenish, chocolate brown. He looked at the walls beside him, both of which were so close that they touched both of his elbows. On the starboard side was a glory hole and on the port side a piece of gum had been stuck onto the wall and formed into the shape of a nipple, surrounded by the words "This is the only tit you'll see today, squid." He did not, however, see any of that thin, pulpy shit paper he needed to wipe the smelly residue from last night's Schlitzfest from his hind quarters. Even the shitpaper holder had been ripped from the wall. In its place were the letters 'F.T.N.' Shortshank sighed and said, "You got that right.'