fanoogie; fenugie noun during the Vietnam war, a soldier freshly arrived in Vietnam US A back formation from FNGFUCKING NEW GUY
— Linda Reinberg, IntheField, p. 78, 1991
Franks was what the troops called a “fanoogie,” abbreviated as FNG and standing for “f’ing new guy.” It was a way for veterans to set themselves apart from the newcomers and to tell the new guys that they had lots to learn[.] — Tom Clancy with Fred Franks Jr., IntotheStorm, p. 26, 1991