Treehouse is the product development division of Nintendo of America[1]. Though the name is often used to refer solely to the localization department, "Treehouse" englobes the localization team, audio-visual department, product management and quality assurance work[2].
Treehouse handles English translations as well as French, Spanish and Portuguese[3] localizations for the North American market. Treehouse started as an initiative to address the lackluster quality of the English localization of Nintendo games during the 8-bits and 16-bits era[2]. The department often translate games as they are being developed and thus often communicate with the Japanese development teams [1]. The Japanese developers also consult Treehouse to prevent overly Japanese-specific cultural content from being included in the games, as to ensure Nintendo games have an "international" feel[2].
The "Treehouse" name finds its root in Donkey Kong Country; the team handling the North American localization of the game was "locked away" from the rest of NOA due to Nintendo's high secrecy toward the game and was codenamed "Treehouse" after Donkey Kong's Treehouse[2]. As Treehouse expanded, the name stuck.