What's the origin of the idiom "to be left holding the bag"?
According to the Online Etymology Dictionary:
To be left holding the bag (and presumably nothing else), "cheated, swindled" is attested by 1793. Many figurative senses [of bag], such as the verb meaning "to kill game" (1814) and its colloquial extension to "catch, seize, steal" (1818) are from the notion of the game bag (late 15c.) into which the product of the hunt was placed.
The American Heritage Dictionary of Idioms:
This idiom grew out of the earlier give one the bag (to hold), which dates from about 1600 and alludes to being left with an empty bag while others have taken the valuable contents.
Etymologies given by resources that focus on a more general audience:
The Whole Ball of Wax and Other Colloquial Phrases:
The American form may come from the old confidence trick known as the drop game (q.v.) in which the sucker is left holding a (hand)bag filled with worthless paper
Safire's Political Dictionary:
a snipe hunt is an elaborate practical joke in which the victim is left in a lonely field at night holding a sack and a tennis racket, one origin of the phrase left holding the bag;
Idioms in the News - 1,000 Phrases, Real Examples:
As early as the 1500's, to give the bag (to someone) meant to leave them quickly. An early example that is close to the modern phrase was written in 1793 by Thomas Jefferson: "...if the bankruptcies of England proceed...she will leave Spain the bag to hold..."
In BrE it's actually more likely to be baby, not bag...
As with the AmE corpus (where bag is 10-15 times more common than baby), the usage didn't take off until early C20. Here are the earliest three instances of left holding the baby in Google Books (1905-1912), all of which put the expression in "scare quotes" - a very strong indicator that every one of those writers thought the expression was relatively new and/or might be unfamiliar to their readers.
Personally, I think the allusion to a woman being left to deal with the consequences of unplanned pregnancy alone would connect with the average person far more than criminals facing arrest, and foisting their swag bag on the most "expendable" (dumbest?) member of the gang.
But presumably that's because I'm a Brit, which is why my preferences are reflected in the extreme US/UK usage split on this one.