Cahoot is used almost exclusively in the phrase "in cahoots," which means "in an alliance or partnership." In most contexts, it describes the conspiring activity of people up to no good. (There's also the rare idiom go cahoots, meaning "to enter into a partnership," as in "they went cahoots on a new restaurant.") "Cahoot" may derive from French cahute, meaning "cabin" or "hut," suggesting the notion of two or more people hidden away working together in secret. "Cahute" is believed to have been formed through the combination of two other words for cabins and huts, "cabane" and "hutte."
1827, in the meaning defined above
perhaps from French cahute cabin, hut