Job 39:9

This is the wild ox, not the tame or domesticated ox. "Extinct since 1627, this enormous animal was the most powerful of all hoofed beasts, exceeded in size only by the hippopotamus and elephant. It was hunted by the Assyrians and is probably to be identified with the aurochs" (Zuck p. 171). Such an animal, even though strong for plowing, would not even spend one night in Job's barn (Job 39:9), neither could he be trusted to work the fields (Job 39:11-12). "Because Job could not effect so small. change as taming. wild ox and using it in his farming, the implication becomes explicit: Job certainly could not alter the Creator's ways nor manage His universe!" (p. 172).

"The translators of the Septuagint rendered re'em by the Greek term monokeros (one horn) on the basis of the relief representations of the wild ox in strict profile, which they found in Babylonian and Egyptian art. It thus found its way into the KJV as 'unicorn'" (Jackson pp. 82-83).