Abarim Publications' online Biblical Greek Dictionary
The noun κρανιον (kranion) means skull, or more specifically the brain box, hence the English word cranium. It stems from the unused noun καρα (kara), meaning head, top or peak, which in turn derives from the widely attested Proto-Indo-European root "ker-", which mostly yields words that have to do with horns (see below).
The noun κερασ (keras) means horn and stems from the Proto-Indo-European root "ker-". This root is also suspiciously similar to the Hebrew noun קרן (qeren), meaning horn, which comes from the verb קרן (qaran), which either means to have horns, or to radiate — this is the verb that describes how Moses' face radiated when he came from the mountain (Exodus 34:29).
It's not clear whether the Hebrews saw horns as rays, or rays as horns, or whether the PIE language basin got this word from the Semites or vice versa (which would probably mean that one of the two lost its own native word for horn), but PIE does not have the ray-clause, and instead equates the horn with the top of the head; hence the word κρανιον (kranion), cranium, which literally means place of the horns, even though humans have no (visible) horns.
But in the PIE basin (and particularly in the Latin branch), horns became proverbial for strength and courage (in rhetoric, the horn of an argument was its most salient point). The horn also acquired a sexual connotation, but curiously negative, namely to signify a cuckhold (that's the husband of a promiscuous wife). The husband would be described as growing horns (becoming horny), whilst someone else's offspring would grow within his wife, for him to provide for.
The Hebrews made trumpets from horns, and used them to incite people into action. The Indo-Europeans associated horns with the overstepping of boundaries. The overlap lies in the extension of the range of one's own control into that of another, which is precisely what language is designed to do, and language is the vehicle of reason, the substance of which is light.
This would suggest that the familiar image of the cornucopia (the overflowing horn) factually tells of an overflowing mind, that the Horn of Salvation of the House of David (Luke 1:69) is the alphabet (see our article on the name YHWH), that the horns of Joseph (Deuteronomy 33:13-17) are the meanings of dreams (see our article on οναρ, onar, dream), and that the ram caught in the thicket on Mount Moriah, the future temple mount, reflects the beginning of the spread of literacy in the human world (and see our article on the name Isaac for a brief look at this difficult scene).
Note the obvious similarity between the verb קרן (qaran), to radiate, and the verb קרא (qara'), to call near (hence the name Quran). Another verb that means to radiate is הלל (halal), hence the familiar term Hallelujah, which may have helped form the name Hellas, or Greece.
Our noun κερασ (keras), horn, is used 11 times in the New Testament, see full concordance, and from it derive:
- The noun κεραια (keraia), meaning something like horniness or hornishness, which in the classics could describe anything pointy, protruding or horny (from insect antennae to big wooden beams, bones, branches, mountain tops, the points of the lunar crescent and projecting landmasses such as the "horns" of Africa and Europe on either side of the Strait of Gibraltar). This word occurs in the New Testament in Matthew 5:18 and Luke 16:17 only, both times in Jesus' assertion that heaven and earth would fail before one κεραια (keraia) of the law would. This is traditionally explained to refer to something very small, also because of the reference to the ιωτα (iota), which is the smallest Greek letter. This is nonsense, of course, as size and importance are absolutely unrelated (Matthew 13:32). Instead, the reference to the ιωτα (iota) is probably a reference to the Hebrew י (yod), or יד (yad), meaning fist, which together with the κεραια (keraia) refer to the two basic building blocks (the bow and arrow, if you will, or consonant and vowel) of the Law: assertions of self-contained truths (יד, yad) and commands that span the will of the commander and the effect in the commanded (κεραια, keraia).
- The noun κερατιον (keration), little horn, which is a diminutive of κερασ (keras), horn. In the classics, this word is used to describe most any smaller horn-like thing, and on rare occasions the cucumber-shaped fruits, or pods, of the carob-tree, which were and are still grown for animal food. Our noun occurs in the New Testament in Luke 15:16 only, where it indeed denotes food for pigs. Still, the story in which this word occurs is highly allegorical, and the little horns that the pigs were eating, while the prodigal son kept watch over them while starving, possibly also refers to the art of writing that the Semites had perfected and now formed the backbone of the Roman Empire (see our article on the name Legion). Note that the name Cornelius means Little Horn