In the 12th century, the village of Rustrel already existed under the name of Rograstrel. It then appeared under the more Provençal consonant of Ruastrello in the cartulary of the church of Apt in 1274 before being francized in Rustrel. Etymologically, Rustrel could come from the Latin ruga (ridge or rocky ridge) accompanied in the older forms of the village's name by the double suffix ast(e)r and elium. Another hypothesis links the name of Rustrel to another Latin word, rocastellum (castle built on a rock), which would correspond to the place called Villevieille leaning against a rocky prong to the northeast of the village.