Where does “արջառ” come from?

արջառ (Armenian) comes from Old Armenian արջառ, from Old Armenian արջն, from Iranian ira, from Proto-Iranian úštrah, from Proto-Indo-Iranian úštras, from Proto-Indo-European úǵtr-o-s, from Proto-Indo-European -os — Creates action nouns or result nouns from verbs;...

արջառ (Armenian): young bullock