Passage 8.34.1
ἐκ δὲ Μεγάλης πόλεως ἰόντι ἐς Μεσσήνην καὶ σταδίους μάλιστα προελθόντι ἑπτά, ἔστιν ἐν ἀριστερᾷ τῆς λεωφόρου θεῶν ἱερόν. καλοῦσι δὲ καὶ αὐτὰς τὰς θεὰς καὶ τὴν χώραν τὴν περὶ τὸ ἱερὸν Μανίας· δοκεῖν δέ μοι θεῶν τῶν Εὐμενίδων ἐστὶν ἐπίκλησις, καὶ Ὀρέστην ἐπὶ τῷ φόνῳ τῆς μητρός φασιν αὐτόθι μανῆναι.
From Megalopolis, on the road to Messene, after advancing about seven stades, there is situated on the left side of the highway a sanctuary dedicated to goddesses. Both the goddesses themselves and the district around their sanctuary are called Maniai ("Madnesses"). It seems to me that this epithet refers to the Eumenides, and they say that it was at this very place that Orestes became mad because of the murder of his mother.