It is actually spelled "porte cochere", and is French for "coach door". It's original (1698) meaning was for a porch-like structure at an entrance to a building where a horse and carriage can pass through. It has been expanded to refer to a roofed structure that covers a driveway or at the entrance of a building that provides shelter for people entering or exiting a vehicle. A porte chochere is different from a carport in that vehicles do not park under them. In western culture, "porte cochere" is often spelled and pronounced "porta cache".
See:
http://www.merriam-webster.com/dictionary/porte+cochere
http://www.buffaloah.com/a/DCTNRY/p/porte.html