In the Theological Dictionary of the Old Testament, Volume 13 (1973), H.P. Muller (with some assistance by J. Tropper) has an excellent article on the meaning of the Hebrew word, “Reem.” Muller thoroughly evaluates the question of the meaning of the word, Reem, leaving little additional to be said. I would note, for example, that Muller’s Semitic analysis does not contain analysis of the Moabite language. I suspect that the reason for this omission is that there is very little Moabite language material available, and it has been argued that Moabite is basically a dialect of Hebrew. As can be seen from this article, not only is it fairly clear what Reem means in the cognate languages, but there are even examples of places where bull and and reem are used in poetic parallels, as in some of the Scripture texts. One interesting text refers to Baal as the “cloud rider,” which would seem to fit well with the idea of the Moabites referring to Baal as the god of thunder.

Although not immediately visible from the chapter summary, Muller addresses the phonetically similar but irrelevant Arabic reem.

On the other hand, Muller raises the interesting point that the Geez (an Ethopian language) word reem can refer to wild bull, rhinoceros, and unicorn.

While Muller’s Biblical analysis seems generally correct, there are aspects that could be further supplemented. For example, in Psalm 22, Muller overlooks the previous introduction of lion, dog, and bull in the same psalm.