Today Greek is a Balkan language. Latin in the form of Romanian is also a Balkan language. Greek, Romanian and, in Bulgarian, the pronouns fuse Dative and Genitive.
My idea of how this originated is through Latin having double function Dative/Genitive forms like "puellae" or "diei".
"Do librum puellae" - I give the girl a book.
"Liber puellae impressus est, non manu scriptus" - The girl's book is printed, not a manuscript / not handwritten.
"Inceptio diei mane appellatur" - The day's beginning is called morning.
"Diei dominicae maxima debetur reverentia, tota hebdomade" - The greatest reverence is owed to Sunday, in all the week.
Greek and Bulgarian caught on to this and Latin going to Romanian then generalised this fusion of the two cases, by bilingualism.
Now, today the bilingualism between "Latin" (as in Romanian) and Greek is very restricted even on the Balkan and restricted to the Balkan.
However, this was not always so. In Palestine, during the British mandate, Megiddo prison was built over a Christian house. I just learnt this from Jonathan Sarfati today.*
I totally agree with the theological implications of this very ancient Christian house, Jesus Christ is called God, this is in a mosaic which has so far been dated to AD 230 - well near a century before the Council of Nicea.
However, I will also concentrate a bit on the grammatical side.
Quorting Sarfati's article:*
Notice at the end of the second-last line, there are words with a line over them. These are an ancient space-saving convention called nomina sacra (singular nomen sacrum), ‘sacred names’.8 That is, names for God would be abbreviated to the first and last letter, and a line drawn over them to indicate the shortening. These are found in many early papyri of the New Testament, and in a number of icons. In this mosaic the nomina sacra are clear. They are ΘΩ, ΙΥ, and ΧΩ. They are, respectively, the first and last letters of ΘΕΩ/Θεῷ (Theō, dative of Theos, God), ἸΗΣΟΥ/Ἰησοῦ (Iēsou, genitive of Iēsous, Jesus), and ΧΡΙΣΤΩ/Χριστῷ (Christō, dative of Christos, Christ).
So, genitive and dative are mixed here, about same referent?
Wait a little minute ... in Greek, if I recall it correctly, Ἰησοῦς has a rather special declinsion.
Ἰησοῦς, Ἰησοῦ, Ἰησοῦ, Ἰησοῦν, Ἰησοῦ.
Genitive, Dative and Vocative coincide. Nominative sticks out by having an s and Accusative by having an n.
So, in the inscription, we could actually instead of dealing with an early case of Genitive and Dative fusion, simply be dealing with one of the Greek confluents to this fusion. In the feminine, I think Dido has a similar reduced scale of cases, as Greek was previously also enjoying or suffering in the Dual number.
Hans Georg Lundahl
Passion of St Longinus
Caesareae, in Cappadocia, passio sancti Longini militis, qui Domini latus lancea perforasse perhibetur.
PS, it seems my Greek was rusty ... I was right about Jesus' Holy Name, I suppose, but wrong about Dido. Διδω, Διδους is at least the most common Greek declinsion of that name./HGL
* CMI : Early mosaic calls Jesus ‘God’
by Jonathan Sarfati, Published: 15 March 2018 (GMT+10)