Vasileiadis, “The pronunciation”, 16–20: Ἰαῶ, Ἰαοὺ, Ἰευώ, Ἰεωά, Ἰηουά, Ἰαβά, Ἰωβὰ, Ἰεωβὰ, Γεοβά, and Ἰαχωβᾶ.
I'm honing in on Time and Place, re: Hellenistic Judaism of the Diaspora 100 BC - 200 AD.
If - from another thread - we accept that Philo of Byblos' Sanchuniathon
1) properly dates c.135 AD, and
2) derives from at least 'somewhat older' (c.115 AD) Temple documents shared by a local "Priest of Ieou" {Ἰεωά},
3) the local Jewish "Ieou" cult was not new in 135 AD, therefore present in the vicinity of Byblos before 100 AD,
4) repeated and emphatic references to Thoth from data suggests a Serapis (Alexandrian Library/scribal) connection,
then we can admit the strong likelihood that IN BYBLOS c.100-120 AD a heterodox Jewish "Ieou" cult
already possessed Hermetic texts and Gnostic tendencies. IN BYBLOS, outside Alexandria and (the Fayum) Egypt ... where the Hermetica had originated in its primitive elements, c.100-150 years before, or at least c.50 BC if not earlier.
I've seen no evidence there were Jewish cults active in Egypt after 115 AD; any Egyptian Jewish Ieou materials should pre-date the pogroms. I cannot see Jewish cultaic works imported into the Fayum later; it's wrong to assume that. But local Gnostics might have exploited older Jewish writings re-discovered several generations later.
Given all this, dating the oldest parts of the Books of Jeu (Ieou)
c.200 AD seems reasonable. 'Books of Jeu' is a misnomer, misleading: it's 3rd C. Xtian Gnostic material (not Jewish). Textual emendations and Christianizing additions to this popular work led
Mead [1906] to 'late-date' the work c.300 AD. Nothing supports the idea any vital, operative 'Ieou cult' existed in Egypt c.200 AD - far too late and almost 100 yrs after any such would have disappeared. Ieou material in Egyptian documents c.200 AD is anachronistic, dislocated.
In the Pistis Sophia, where (Alexandrian) Melchizedek material is re-cycled, some early and original 1st C. AD Egyptian Jewish material might be revealed. As an exalted psychopomp, (orig. Phoenician) Melchizedek purified and liberated souls, the Jewish alternative to Hermes Trismegistos/Poimandres. I've seen no evidence of
Melchizedekianism in Northern Semitic materials: M. looks almost purely Judeo-Egyptian, possibly exported to a few Diaspora synagogues before 115 AD. However, Melchizedekianism conflicted more than corresponded with (Judeo-)Hermeticism in this period, as these would have been competing Jewish and Judaic cults. A resurgence of literary Melchizedekianism (i.e. spotty reports of Late Antiquity, among heresiologists) seems more imaginary, literary fiction. Among Diaspora Jews in the 3rd and 4th C. AD, Yahoel and then Metatron appear as the prime intermediaries. Melchizedekianism had long since been in decline, replaced inadequately by a Moses Savior cult (c.275 BC) then effectively and ever more by the radical Christos Savior cult (c.10 AD?), or the swelling Serapis (Hermetic) cult in Alexandria (40 AD -). New gods took over as the old Phonecian god Melchizedek faded then disappeared among Jewish groups in the 1st C. AD.
This is to say any Gnostically-divergent "Ieou Priesthood" (antinomian Judaism) outside Egypt after 100 AD wasn't likely to have been 'Melchizedekian'. On the contrary, scorned Melchizedekianism was rapidly disappearing after 75 AD. And all this is to explain why most (Judeo-) Gnostic systems across the Diaspora developed alternative (dissimilar) Jewish elements... and converted so quickly to the most popular (Jewish) Xtian cult.
The donkey-call of 'Yao, Yao' (braying Jews?) sounds anti-Jewish, but "Alexamenos worships [his] god" would be a Roman graffito playing upon (Late First/Early Second C. AD) 'Sethian' misconceptions to
slander (Egyptian?) Judeo-Christians. Curious!