An animal called the re’em (Hebrew: רְאֵם) is mentioned in several places in the Hebrew Bible, often as a metaphor representing strength. "The allusions to the re'em as a wild, un-tamable animal of great strength and agility, with mighty horn or horns (Job xxxix. 9–12; Ps. xxii. 21, xxix. 6; Num. xxiii. 22, xxiv. 8; Deut. xxxiii. 17; comp. Ps. xcii. 11), best fit the aurochs (Bos primigenius). This view is supported by the Assyrian rimu, which is often used as a metaphor of strength, and is depicted as a powerful, fierce, wild mountain bull with large horns." This animal was often depicted in ancient Mesopotamian art in profile, with only one horn visible.
The translators of the Authorized King James Version of the Bible (1611) followed the Greek Septuagint (monokeros) and the Latin Vulgate (unicornis) and employed unicorn to translate re'em, providing a recognizable animal that was proverbial for its un-tamable nature. The American Standard Version translates this term "wild ox" in each case.