Gargun was the common term for Orcs (or their eastern kindred) in southeastern Middle-Earth, especially the Shelf-lands of Lôkhas Drûs.The term itself derived from Brâric, a language related to the Drûghic-Speech.
The name seems to be related to drûghic "Gorgûn" and possibly to "Gark" and "Karku" as well.