Abarim Publications' online Biblical Hebrew Dictionary
The verb קרן (qrn) is a bit of a mystery. It occurs in several Semitic languages and it always has to do with horns or having horns. In Hebrew, curiously enough, it may also mean to shine or be radiant. Although there's an obvious imaginary overlap between being radiant and having horns, in cognate languages this root only means to have horns. But we know that the Hebrews used this verb in the meaning of to shine because it was applied to Moses when he came down the mountain after his meeting with God (Exodus 34:29). The Vulgate had Moses grow horns in this passage, and that's why Michelangelo's famous statue of Moses shows him with horns.
This verb comes with a noun, namely קרן (qeren), meaning horn, and that's peculiar too. Why is there a noun that means horn, and not a noun that means ray? (Although, Habakkuk 3:4 speaks of rays (probably not horns) that emanate from the Lord's hand.)
HAW Theological Wordbook of the Old Testament thinks that the verb was derived of the noun, while BDB Theological Dictionary says that the verb and the noun were both derived of an even more fundamental root, but the meaning of this most fundamental root is even more obscure.
A similar duplicity may exist in the verb צוץ (sus), which means to bloom or to shine.