ὀπισθοκράνιον
From LSJ
ἔστιν δέ που ἡ μὲν ἐπὶ σώμασι γυμναστική, ἡ δ' ἐπὶ ψυχῇ μουσική → I think I am right in saying that we have physical exercise for the body and the arts for the soul
English (LSJ)
[ᾱ], τό, the back part of the skull, occiput, Sever. ap. Aët.7.92, Paul.Aeg.6.2, Glossaria.
German (Pape)
[Seite 358] τό, der hintere Teil des Hirnschädels, VLL.
Greek (Liddell-Scott)
ὀπισθοκράνιον: τό, τὸ ὄπισθεν μέρος τοῦ κρανίου, τὸ ἰνίον. Γλωσσ.· οὕτως, ὀπισθόκρᾱνον, Νικηφ. Βλεμμ. Ἐκλογ. σ. 667, ἔκδ. Mai.