c.1200, bagge, from Old Norse baggi or a similar Scandinavian source; not found in other Germanic languages, perhaps ultimately of Celtic origin. Disparaging slang for "woman" dates from 1924 (though various specialized senses of this are much older). Meaning "person's area of interest or expertise" is 1964, from Black English slang, from jazz sense of "category," probably via notion of putting something in a bag.
To be left holding the bag (and presumably nothing else), "cheated, swindled" is attested by 1793. Many figurative senses are from the notion of the game bag (late 15c.) into which the product of the hunt was placed; e.g. the verb meaning "to kill game" (1814) and its colloquial extension to "catch, seize, steal" (1818). To let the cat out of the bag "reveal the secret" is from 1760.
An anatomical sac or pouch, such as the udder of a cow.
A container of flexible material, such as paper, plastic, or leather, that is used for carrying or storing items.
[fr game shot and stuffed into the game bag; second sense fr the use of the heavy plastic body bag for the handling of military and other casualties]
brown-bag, dime bag, ditty bag, doggy bag, douche bag, fag bag, fleabag, grab-bag, hair bag, half in the bag, have a bag on, in the bag, jiffy bag, let the cat out of the bag, nickel bag, old bag, rum bag, sandbag, sleazebag, slimebag, stash bag, tie a bag on, windbag