Go to the mattresses

I've heard this phrase from The Godfather, and I know it means to die, but does anyone know the origin of it? Or why it says, the mattresses?

It means "go to war." They buy mattresses to outfit an apartment/house where everyone sleeps until it's over.

"I found an excellent site called organizedcrime.about.com/ cs/glossary which has the greatest glossary of crime terms. They say that to 'go to the mattresses' means 'to go into hiding', (presumably because someone in hiding would just lie on the bed and wait for the heat to go off.)"