During the Middle Ages, Cachan was referred to in Medieval Latin texts as Caticantum, later corrupted into Cachentum, Cachant, and then Cachan. Some understand Caticantum as meaning "singing of the cat", "mewing of the cat", but this is not certain. Some others see a connection with the verb "to hunt" (captiare in Vulgar Latin, chacier in Old French).
Cachan was originally a hamlet within the commune of Arcueil, later renamed Arcueil-Cachan. The commune of Cachan was created on 26 December 1922 when it seceded from the commune of Arcueil-Cachan, which was renamed back to Arcueil.