tldr The expression likely derives from "Foo was here," scrawled by Australian soldiers in the Great War. The precise moniker "Kilroy" is disputed, the prevail

tldr The expression likely derives from "Foo was here," scrawled by Australian soldiers in the Great War. The precise moniker "Kilroy" is disputed, the prevailing theory crediting a technician James J. Kilroy of Braintree, MA who chalked the "easter egg" epigram on panels of WWII battleships (panels which became inaccessible after the ship was fully built).