Named after the towns of Châtillon and Montrouge.
The station lies where Châtillon, Montrouge and Bagneux meet. Châtillon probably comes from the Latin castellum, a diminutive of castrum, ‘fortress’; the town was Châtillon-sous-Bagneux until 1983. Montrouge, first recorded as Rubeo monte in 1194, means ‘red hill’: place-name experts link it to the reddish, clayey soil of its plateau.