TAKE SOMEONE TO THE WOODSHED (MEANING)

Let's say you have been through hell with your last boyfriend. You can say you got to have a happy life at some point during the relationship but from then on he became someone completely different. Now you have recently put an end to all those times of hardships but your boyfriend doesn't seem to understand that. He calls you up on the phone all the time whining for a second chance and saying how sorry he is, but he really has no chance with you this time. Here is a little of what he said the last time he called:

"I've taken myself to the woodshed for the way I treated you, but please take me back. I love you!" But what does he mean by taking himself to the woodshed?

If you take a look at the picture above, you'll see what a woodshed literally is: a small building where wood for burning is stored. I am not sure exactly about the etymology of that expression, but we can imagine it is no fun to be taken to the woodshed. And maybe that is why people say that if you take someone to the woodshed, you are punishing them for something they have done.