What language would be appropriate for texts to be written in about Thor (Forgotten Realms)?

In our LMoP campaign, there is a Cleric whose deity is Thor. He has come across several texts that discuss Thor (myths and religious texts).

What language would those texts most likely be written in?

(I don’t know if this is helpful context, but he is a Wood Elf).

Would Illuski (Nordic) languages be appropriate here?