Derived from infantry slang, Vietnam war era.
Originaly "new meat" and refered to new troops fresh to the field. Sometimes shortened to "noo bee".
"Short timers"(those ready to head back Stateside) and "two digit midgets" (under 100 days left)considered them dangerous or a jinx.
Stay off the noobie, he's gonna go home early.
The noobie was fixing to dee-dee-mao when that shit hit.