Irish pennant noun a dangling thread on a recruit’s uniform US,1941 Marine humour, marine usage.
— Linda Reinberg, IntheField, p. 115, 1991
Charging up and down the line through the barracks, Sergeant Carey pulls a hanging thread–what the Marines call an “Irish pennant”– from the starched camouflage uniform of Tony Wells[.] — Thomas Ricks, MakingtheCorps, p. 107, 1997