The idiom is thought to have originated in the 19th century in the United States. It was first recorded in print in 1848 in the book "The Life and Adventures of Nat Love." In this book, the phrase is used to mean that the person is going to go and fight someone.
Over time, the idiom "got to see a man about a dog" has come to be used in a more general sense. It can now be used to mean that the person is going to do something that is not what it seems, or that the person is going to do something that is illegal or immoral.
Here are some examples of how the idiom "got to see a man about a dog" can be used:
* "I've got to see a man about a dog. I'll be back in a few minutes." (This person is actually going to go and buy some drugs.)
* "He said he had to see a man about a dog, but I think he was just going to meet his girlfriend." (This person is lying about where he is going.)
* "I don't know what she was up to, but she said she had to see a man about a dog." (This person is implying that the woman was going to do something illegal or immoral.)
The idiom "got to see a man about a dog" is a fun and versatile phrase that can be used in a variety of situations. It is a great way to add a bit of humor or intrigue to your conversation.