a fictitious American male, created by American troops who left the inscription “Kilroy was here” on walls, property, etc., all over the world in the years during and after World War II.
U.S. military graffito character dates to 1945 and is said to be either Sgt. Francis J. Kilroy Jr., U.S. Army Air Transport, whose friend or friends began writing his name everywhere as a prank; or war materiéls inspector James J. Kilroy of Quincy, Mass., who wrote "Kilroy was here" on everything he checked.
[kil-roi] 
rɔɪ