Why did Michelangelo's sculpture of Moses have horns on it?

In one of the Greek translations of The Bible, they translated the Word for halo or ray of light as horn. Because of this mistake in translation, a few depictions of Moses from this period, are depicted with horns.

In more recent translations of the bible, this mistake was corrected it now describes Moses as having rays of light.

Anyway, the "horns" in depictions of Moses are supposed to be rays of light.