A phrase taken from a popular joke. To say someone is "in the barrel" or "taking a turn in the barrel" means it's their turn to do an unpleasant task or to suffer an unpleasant experience. The joke is as follows:
A sailor on a Navy ship had been out to sea for weeks, and was beginning to go through sex withdrawals. Fed up with the lack of sex, he asked one of his shipmates what he did when the pressure was too much to take.
"Well, there's a barrel with a hole in it near the mop storage. When it gets to be too much for us, we use that."
So the sailor went over to the barrel and decided to give it a go. Finding it was better than he'd expected, he began using it regularly, and his problems seemed to vanish.
After a couple of weeks, his commanding officer began to take notice, and said, "You seem to be a lot more relaxed. What's your secret?"
The sailor, embarrassed to give a straight answer, simply said he'd been getting better rest.
"Well good, sailor. You're going to need it," replied the officer. "Today's your turn in the barrel."
A popular passtime for Northerners during the late 19th Centuary.
A barrel would be placed in a public place with a selection of holes in it at different heights. The contents of the barrel would normally be a petty criminal who would have to spend a period of time "in the barrel".
Local men would visit the barrel and insert their manhoods into the holes of the barrel until the petty criminal had performed an oral sex act on them.
Judge - "Mr Lock you have been found guilty of the theft of a loaf of bread, do you have anything further to say?"
Mr Lock "Eh up t'honour I was jost a bit t'hungry"
Judge "that is no excuse! Guards take him forth from here and place him IN THE BARREL for 7 days and nights"