The story
Coined by Ian Bogost in response to FarmVille winning an award for "Best New Social/Online Game" at the 2010 Game Developers Choice Awards. The win caused Bogost, a critic of the freemium model used by Zynga, to be struck with the thought: "Games like FarmVille are cow clickers. You click on a cow, and that's all you do." He subsequently developed Cow Clicker, an intentionally simplistic parody game, which itself became a surprise viral hit.
Etymology from Wiktionary, CC BY-SA 4.0.