La expresión a la que tú te refieres, se usa como insulto para demostrar enojo, furia o frustración. Es referirse indecentemente a la madre de alguien.

It's a "bomb" phrase-- not something you want to say to anyone. It is something that you would find more in Mexican culture than other hispanic cultures. They are into swearing more.

Check this link http://en.wikipedia.org/wiki/Spanish_profanity There's the answer. :)