nu + apostrophe at the beginning of Homeric verses?

Question

I need help understanding a passage from Chantraine's Grammaire Homérique (chapter XVIII, p. 222).

Chantraine talks about the Ζῆν and Ζῆνα forms of the name Zeus. According to Chantraine, the aoidoi felt that its accusative was Ζῆνα and not Ζῆν, which was monosyllabic and only poorly characterized the accusative.(*)

What bothers me is this extract(**) (my translation):

The form Ζῆν is used only under certain conditions: either before vowels [...] or at the end of a verse, but when the next verse begins with a vowel; in this case some of the best manuscripts [...] write Ζῆ and add at the beginning of the next verse " ν' " (i.e. nu + apostrophe).

I don't understand where this idea of adding at the beginning of verse ν' [nu + apostrophe] comes from: is it a word with apocope? But which one? As it stands, the Homeric text knows no verse beginning with ν'. As far as I know, there is no word in Homeric Greek that can correspond to ν'. On the other hand, it seems strange to me to cut a word so as to divide it into two parts (Ζῆ | ν), each part belonging to a different verse (Ζῆ + ν).

How then can we understand Chantraine's remark?

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(*) "Les aèdes qui ont combiné les formules homériques devaient déjà avoir le sentiment que l'accusatif était Ζῆνα. Ζῆν présentait le double inconvénient d'être un monosyllabe et de caractériser médiocrement l'accusatif"

(**) "Cette forme archaïque est proprement homérique mais déjà dans l'Iliade et l'Odyssée elle n'est employée que dans certaines conditions : soit devant voyelle (E756 [...]), soit en fin de vers (Θ206 [...]), mais lorsque le vers suivant commence par une voyelle (dans ce cas une partie des meilleurs manuscrits [...] écrivent Ζῆ, et au début du vers suivant ν').

Chantraine, Grammaire Homérique (chapter XVIII, p. 222)

Answer 1

According to Hagen 1994, the etymologically expected form of the accusative was Ζῆν (compare Latin diem), but this became Ζῆνα by analogy with regular third-declension nouns. It's unclear if the original author of the epics understood the accusative as Ζῆν or Ζῆνα, or if it was changed through the years in later recitation, or what exactly. Almost all instances of Ζῆν appear before a vowel (e.g. in the set phrase Ζῆν ὕπατον), which some editors take as Ζῆν and others as Ζῆν' with elision; the exceptions come at the end of a line, like in Iliad VII.206, XIV.265, and XXIV.331, and always before a line starting with a vowel.

As Hagen puts it (translation and emphasis mine):

The Hellenistic grammarians Aristophanes and Aristarchus and their school not only accept elision [in these instances] but also put the final consonant (ν) at the beginning of the next verse (Ζῆ/ν'): οἱ περὶ Ἀριστοφάνην τὸν γραμματικὸν καὶ Ἀρίσταρχον … τὸ ν τῷ ἐπιφερομένῳ στίχῳ ἐπετίθεσαν ["those following Aristophanes the grammarian and Aristarchus…move the nu to the following verse"] with the reason: ὅτι ὁ λόγος ἔρρωται ἐπὶ παθῶν ["because the word is strengthened(?) by these modifications"].

[…] According to Körte, in the three relevant passages in the Iliad, "all authoritative manuscripts have assigned the ν of Ζῆν' to the following verse". He terms this phenomenon an "episynalepha".

In other words, according to these grammarians, the only correct accusative was Ζῆνα, never Ζῆν; Ζῆν should always be interpreted as Ζῆν' with elision. Even when it appeared at the end of a line, the followers of Aristophanes and Aristarchus analyzed it as Ζῆ/να, with the word broken in half, so that the alpha could elide into the first vowel of the next line.