Where does “երեսնամյա” come from?

երեսնամյա (Armenian) comes from Old Armenian երեսնամեայ, from Old Armenian երեսուն, from Proto-Indo-European trīḱomt, from Proto-Indo-European tridḱómt, from Proto-Indo-European tri-, from Proto-Indo-European tréyes — three.

երեսնամյա (Armenian): of thirty years; thirty-year; of thirty;...

Definitions

of thirty years; thirty-year; of thirty;...

Ancestry of “երեսնամյա”, step by step

Step	Language	Word	Meaning
1	Old Armenian	երեսնամեայ	Alternative form of երեսնամեան
2	Old Armenian	երեսուն	thirty
3	Proto-Indo-European	trīḱomt	—
4	Proto-Indo-European	tridḱómt	thirty
5	Proto-Indo-European	tri-	three, threefold
6	Proto-Indo-European	tréyes	three

Every word from Proto-Indo-European tréyes →Every word from Proto-Indo-European tri- →Every word from Proto-Indo-European tridḱómt →