Papé Satàn, papé Satàn, aleppe! is a literary quotation and invocation: an exact verse of Dante Alighieri, Inferno, Canto VII. Plutus shouts it when Virgil passes in the original Divine Comedy.
In the Descent, Plutus invokes it on meeting the group, as recognition of a higher authority or a reaction to a strange presence. The verse resounds in the Descent letter for letter, faithful to the seventh canto.