Google "OEM" and this is the first thing that pops up:
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components which are purchased by a second company and retailed under the second company's brand name. It is a form of outsourcing.
Contradictory Definition
Confusingly, OEM may also refer to a company that purchases a component made by a second company for use in its own product, or sells the product of the second company under its own brand name. Companies who follow these practices are better termed value added resellers or resellers, respectively.
If it were an "original" part, it would be listed with the name of the manufacturer (e.g. Porsche, Bosch, etc.).