There is a figure of Moses which was used as the centerpiece of Pope Julius’ II tomb. The artist Michelangelo, sculptured that statue and the Catholic Church proudly displays it now in the Church of St. Peter in Rome.
What makes this statue so different is that Michelangelo put horns on top of Moses’ head. This is but one of many statues and pictures of Moses portraying Moses with horns. Why did people 450+ years ago make this assumption?
In the Jewish Exodus story, Moses comes down from the mountain after getting the second set of tablets, the Ten Commandments, from god ― the Invisible Man in the Sky. The bible story relates that Moses didn’t know that his face was radiant because he had spoken to God.
"... when Moses came down from mount Sinai with the two tables of testimony in Moses' hand, when he came down from the mount, that Moses wist not that the skin of his face shone while he talked with him. (Exodus 34:29 KJV)
And it came to pass when Moses descended from Mount Sinai, and the two tablets of the testimony were in Moses' hand when he descended from the mountain and Moses did not know that the skin of his face had become radiant while He had spoken with him (Exodus/Shemot 34:29 Judaica Press Complete Tanach)
In Hebrew, the word for “radiant” is heban. קָרַן, an expression meaning horns (קַרְנַיִם). According to Rashi (1040-1105CE), the Jewish preeminent biblical commentator, this word was used because "light radiates and protrudes like a type of horn." Jews claim that when the Hebrew bible was translated into Latin (not Greek), the translation was that Moses’ face “was horned.” In fairness, this explanation seems stretched, because a man's face is large, round or oval in shape. If radiant, the whole face would glow, not in two separate protrusions column-like horns. Specifically, the Septuagint or Greek version of the Hebrew bible (3rd-1st century BCE) translates this phrase as "his face was glorified." Conversely, Saint Jerome's Latin Vulgate translation (5th century CE) was cornuta esset facies sua "his face was horned."
The Christian New Testament has a reference to Moses appearance:
"...Moses, which put a veil over his face, that the children of Israel could not stedfastly look to the end of that which is abolished." (2 Corinthians 3:14 KJV)
"Moses, who would put a veil over his face to keep the Israelites from gazing at it while the radiance was fading away." (2 Corinthians 3:14 NIV)
A visual representation of Moses with horns may have contributed to people's fears that Jews have horns, just like artist representations of the mythical Christian devil. The words in the New Testament are where non-Jews get the impression that Jews are born from the devil and belong in hell (another Christian invention). For example, the book of John has Jesus saying:
“Ye are of your father the devil..." (John 8:44-45 KJV)
"Men in general are quick to believe that which they wish to be true." -Julius Caesar (100 BCE-44 BCE), De Bello Gallico