Where does “Գայիանէ” come from?

Գայիանէ (Old Armenian) comes from Latin Gaianus, from Latin gaius, from Proto-Italic *Gāwjos, from Proto-Indo-European geh₂w- — to rejoice.

Ancestry of “Գայիանէ”, step by step

Step	Language	Word	Meaning
1	Latin	Gaianus	—
2	Latin	gaius	—
3	Proto-Italic	*Gāwjos	—
4	Proto-Indo-European	geh₂w-	to rejoice

Գայիանէ — Etymology, Origin & Word History | Etymology Explorer