Green’s Dictionary of Slang

1. (US) one who takes a packed lunch to school or work.

1954		Gazette-Times (Corvallis, OR) 17 Sept. 2/2: The ‘brown-baggers’ will not be eating in the gymnasium this year , since space for 100 more students has been added to the cafeteria.
1956		‘More USAF Sl.’ AS XXXI:3 227: brown-bagger , n. Originally a married person who brought his lunch in a brown paper bag. Today, a common term for any married man.
1964		Troy Record (NY) 16 Jan. 30/5: If your husband as a ‘Brown-bagger’ (Trans. carries his lunch in a little brown bag) this story is not for you.
1978		H. Selby Jr Requiem for a Dream (1987) 78: The nine to fivers, the brown baggers, the strap hangers, the working stiffs.
1994		N. McCall Makes Me Wanna Holler (1995) 34: Dudes joned brown baggers about being too poor to buy school lunches.
2000		Star-Democrat (Easton, MD) 6 Sept. 27/1: I’m a brown-bagger too, and I know what a trick it is to pull it is to pull together lunches day after day.
2011		Des Moines Register (IA) 4 Dec. 110: [advert] This cheery thermos is sure to make that brownbagger’s deskside lunch much more stylish.

2. (US campus) an excessively hard-working student [the brown bag contains books rather than lunch; or the packed lunch means one can stay at one’s desk working rather than take a break].

1962		L.A. Times 5 July 38/5: A lunch hour course in human behavior [...] at USC’s downbtown campus [...] is known as the ‘Brownbagger Special’. Students listen to lectures while eating their sack lunches.
1990		(ref. to 1950) W. Safire Lang. Maven 17: The deskbound undergraduate has been [...] damned as [...] a brown bagger.