Green’s Dictionary of Slang

(US) a bag for one’s belongings.

1936		R.F. Adams Cowboy Lingo 37: He carried his personal effects [...] in his ‘war-bag.’.
1948		N. Nye Breed of the Chaparral (1949) 52: I should hate to see you packin’ your warbag [...] More than one can play at this flip-and-shoot business.
1955		W. Henry Who Rides with Wyatt 75: Ferd held the lamp and watched him rummaging in his warbag.
1975		J. Knap Family Camping Hbk 85: The Personal Warbag It may seem silly to write about the personal items that should be taken along [etc.].
1982		M. Braun Judas Tree (1983) 97: As he soaped his hands his gaze was attracted to his warbag. He always left it on the floor beside the washstand.
2003		Black Belt May 133: [advt] Warbag &Warbag-Plus. Carry All Your Gear!