So (oph)aiym, "branches" is Aramaic. What does that say (if anything) about
the origin and date of Ps. 104?
Not much by itself. Particularly in poetic texts such words can arise
either as loans (which can suggest something about the date) or as rare
Hebrew words that happen to be more common in foreign cognates. You'd
have to look at a larger sampling of possible indicators to say much
about how this word affects the dating.