ἔερθαι: valid verb form? What verb?

Question

This is l. 28 (the last line) of P.Sapph. Obbink:

I read it as:

ΝΘ̣€Ρ+ . . +Ι̣

where the uncertain theta could be an epsilon (Obbink reads €̣) and the pluses denote a blank spot in the papyrus, thus equivalent to a lacuna, but not due to a hole in the papyrus AFAICT. I am pretty sure I saw ἔερθαι or something like that (perhaps ἔερθε) somewhere, so I go ahead and complete:

]ν ἔ̣ερ+θα+ι̣.

But, there is a problem: I cannot for the life of me find a citation form for this supposed verb. Perseus gives nothing for εερθαι, ερθαι, ηρθαι, and my dictionary has nothing that suggests this form as far as I could find yesterday. The closest thing I can find is αἴρω > ἀέρθαι, but that alpha would probably not turn to an epsilon in Sappho (by whom the poems on the papyrus are), and I even found a contraction of this to ἆρθαι in the line Οὔδεν ἄδομ' ἔπαρθ' ἄγα[ν ἐπ' ὄλβῳ (aka Οὔδεν ἄδομ' ἔπερθα γᾶ[ς ἔοισα if you're reading Campbell), found in this poem. So is this actually a valid Greek verb form, or did I dream of seeing it? And if the former, what is the dictionary form of this verb? And is this an aorist infinitive as I would guess from the -αι at the end? What voice (active, middle, passive)?

Note

When I say "somewhere", I'm not implying it should be in something related to this poem, or even to Sappho. In fact, my vague memory suggests Iliad or Odyssey. I ruled out the former by searching each and every book of it as present on Greek Wikisource for ερθ and coming back with loads of ύπερθε (with or without prefixes) and other irrelevant words, and Googling έρθ on site:el.wikisource.org and not finding anything from Homer. Googling ἔερθαι returns no results, and Googling ἔερθε returns stuff I have yet to browse through.

Answer 1

Given I couldn't find ἔερθαι or ἔερθε via Google nor on the TLG, and the commenters have no miraculous ideas as of now, I must conclude I imagined this form. Too bad.

Supposing this is a verb form, the ending -αι is likely. Starting from εερ . αι, one can feed in μ, σ, τ, getting ἔερμαι, ἔερσαι, ἔερται. These are the singular indicative perfect middle-passive of εἴρω, respectively first, second, and third person. This verb means "to fasten in rows" or "to say" or "to ask".

Answer 2

The closest thing I can think of is ἐέρσαι, which I guess is pronounced like ἐέρθαι if you have a lisp.

Less likely, but If the theta was definitely there, perhaps you forgot a nu and were remembering ἔνερθε(ν)? I doubt it, because it's such a common word that one would hardly forget, but I figure I'd mention it anyway just in case.

Meanwhile, ἐέρσαι is found only in the Iliad at 14.351:

τῷ ἔνι λεξάσθην, ἐπὶ δὲ νεφέλην ἕσσαντο
καλὴν χρυσείην: στιλπναὶ δ᾽ ἀπέπιπτον ἔερσαι.