Here's why the term might be used:
* Pigs are often associated with dirt and uncleanliness.
* Pads can refer to a place where someone lives.
So, "pig's pad" is a playful way of saying that a place is not very tidy.
Here are some examples of how the term might be used:
* "My friend's apartment is a total pig's pad."
* "I'm not sure how anyone can live in that pig's pad."
Important Note: While this term is often used in a humorous way, it can be offensive if you use it to describe someone's home without their consent.