Mopar (MOtor PARts) was originally known as Chrysler Motor Parts Corporation, and was created in 1929 by Chrysler as its parts company.
I'm not sure exactly when, but eventually the name was changed to Mopar. During the '60s with the heightened interest in "factory hot rods" the name Mopar itself became synonymous with the Chrysler Corporation cars themselves due to the popularity of factory "go-fast" parts.
Mopar continues to this day as Chrysler Group's parts division. They carry "performance" parts, OEM replacement parts and other accessories, and are nothing like Ford's Special Vehicle Team, which just tweaks Ford cars to make them faster and does not sell parts (to my knowledge).
(For your personal enlightenment, Chrysler Canada also used the name Autopar (AUTO PARts) up until the 1990's as its factory parts division)
