Over a barrel
What's the meaning of the phrase 'Over a barrel'?
To be 'over a barrel' is to be left without choice; in someone else's power.
What's the origin of the phrase 'Over a barrel'?

barrel' and this is where the expression
derives from.
This is an American phrase and first appeared in the late-19th century. It alludes to the actual situation of being draped over a barrel, either to empty the lungs of someone who has been close to drowning, or to give a flogging. Either way, the position of helplessness and in being under someone else's control is what is being referred to.
An example of such a literal "over the barrel" experience was recorded in the Delaware newspaper The Daily Republican, July 1886, which reported the initiation ceremony of a college fraternity:
He was bound hand and foot and rolled over a barrel. Next he was stripped naked and placed upon a cake of ice... and branded on his back with the fraternity emblem.
Soon after that 'over a barrel' took on the figurative meaning of 'in trouble; without any hope of deliverance. This usage is recorded in The Seattle Post-Intelligencer, January 1893, in a story of an unfaithful wife:
The good, true, loving wife she appeared to be, being, to use a slang phrase "over a barrel." The woman who is "over a barrel" was Mrs. Nellie Brundage, and the man "not her husband" was S. R. Clute.
The modern-day usage of 'over a barrel' has softened somewhat. It is now used to refer to anyone in a situation where they have little choice.