From Dodge Wiki
Mopar (short for MOtor PARts) is the Auto part and Auto mechanic arm of Chrysler LLC. The term was first used by Chrysler in the 1920s and has been in continuous use ever since. Mopar parts are Original equipment manufacturer parts for Chrysler vehicles.
Mopar has passed into broader usage among car enthusiasts as an unambiguous reference to the Chrysler parent company, as the Chrysler name also refers to a company Marque. The term has thus become an inclusive word for any Chrysler-built vehicle — most any Dodge, Chrysler, Plymouth, Imperial, or DeSoto, plus Jeeps and American Motors Corporation vehicles built after Chrysler's 1987 buyout of AMC-Jeep. Thus, for example, a car club for owners of any Chrysler Corporation vehicle might describe itself as a club for "Mopar enthusiasts."