Originating from World of Warcraft. A Chinese gold farmer power levels their character to 60 (or highest level depending if you read this after expansions). Then this character runs instances or certain sections of Kalimdor and the Eastern Kingdoms. They kill and gather anything to make a profit. Their goal is to obtain a steady flow of cash; produce things to sell at the Auction House like a farmer would a crop to market hence classifying them as farmers. A guild known as PK Wang was notorious for this; this could explain the Chinese addition to the term "Chinese Gold Farmer" since the word Wang has been used as a Chinese name for fictional characters such as "Wang Chung". Chinese gold farmers also spend a great deal of time in Orgimmar or Stormwind City spamming their items over and over again.
Farmer yells: “WTS Magister's gloves, Devout Bracers, Flawless Arcanite Rifle, Arcanite Reaper and Heartseeker PST with offers!!"