[1] However, a popular theory identifies James J. Kilroy, an American shipyard inspector, as the man behind the signature.

"[4] During World War II, Kilroy worked at the Fore River Shipyard in Quincy, Massachusetts, where he claimed to have used the phrase to mark rivets he had checked.

Among the ships that Kilroy said he inspected were the aircraft carrier Lexington, the heavy cruiser Baltimore and the battleship Massachusetts.

The phrase began to be regarded as proving that a ship had been checked well, and served as a kind of protective talisman.

[5] Before the war, James Kilroy served as a member of the Boston City Council and the Massachusetts House of Representatives.