Boo Koo is an energy rink with a very large amount of caffeine, similar to other energy drinks. Introduced in 2004, it was marketed with the advertising slogan "Boo Koo Means Big" (due to the 24 fl oz can size). The original size of the drink inspired the 24 oz. sizes of Rockstar energy and others. "Boo Koo" is a rough anglicization of the French word "beaucoup".