ἑπταέτις
From LSJ
τίς δ' οἶδεν εἰ τὸ ζῆν μέν ἐστι κατθανεῖν, τὸ κατθανεῖν δὲ ζῆν κάτω νομίζεται → who knows if life is death, and if in the underworld death is considered life
German (Pape)
[Seite 1012] ιδος, ἡ, fem. zu ἑπταέτης, Ep. ad. 727 (App. 153).
Russian (Dvoretsky)
ἑπταέτις: ιδος Anth. adj. f к ἑπταετής.