Calque? It is not strange for OCS, acctually there is abudance of such therms. Usually, all theological concpets are translated in such way.
What is strange is that footnote cited in OP, does not refere to documents where it is usde, and obviously for some reason mistake wife and concubine.

Huge typo, I wanted to say that it wouldn't be strange for OCS.

Also, another deatal has cought my attention letter ŭ, i.e. ъ, would be strange for Serbian CS.