In the Greek Septuagint, this words is consistently translated as “monokerotos“, which literally means “single-horn”, which is also what the word “unicorn” means. What is interesting is that in St. Jerome’s translation of the Vulgate, he often uses the Latin word “unicornis“, which is where we get the English word, but at other times he uses the Latin word “rinoceros” (rhinoceros), and this is reflected in the Douay-Rheims translation of Numbers 23:22: