Abarim Publications' online Biblical Hebrew Dictionary
The noun כהן (kohen) means priest (Exodus 19:6, Judges 17:5, Joshua 3:13) but it's a noun of unclear origin. It probably originally meant minister or servant, denoting someone who either specifically served a human big-shot or god, or maintained their dwellings.
BDB Theological Dictionary refers to similar Arabic root-verbs, which mean seer or diviner, but also explains that the Arabian priests had a different status and office than Hebrew cohanim. Nevertheless, The Egyptian Potiphera is called a cohen (Genesis 41:45). So are certain Philistines (1 Samuel 6:2) and in Israel, priests of Baal (2 Kings 10:19).
The first time the word cohen occurs is in Genesis 14:18, where it is ascribed to the mysterious Melchizedek, who would be a type of the Messiah to come. It's curious to see that Melchizedek's descent was ostensibly unknown to the author of the story, as much as the origin of his office is to us.
Although in Exodus 19:6 the whole of Israel is called a memelekot kohanim; a kingdom of priests, the priestly caste of Israel was supposed to be filled by the sons of Aaron (Exodus 29:9). However by the time of David, apparently, people from Judah could become priests as well (2 Samuel 8:18). HAW Theological Wordbook of the Old Testament mentions a theory that goes back to the possible original meaning of cohen, namely that of minister or even counselor, and suggests that the priestly function of the sons of David may simply denote servitude to their monarch. But then, when Ezra surveys the people and priests, he remarkably finds no Levites among them (Ezra 8:15). This seems to indicate that, at least after the exile, an entire priestly cast could exist outside the Levite tribe.
Jesus Christ is commonly understood to be of the tribe of Judah, which makes His priesthood a dubious enterprise. But on the other hand, it stands to reason to argue that Jesus wasn't a Jew at all but rather a Levite (see our article Was Jesus A Jew?). Perhaps the priesthood of Jesus refers to His ministry to mankind, and perhaps it denotes His relationship to the Father. Either way, He serves as vicar between the two, just like any cohen.
The noun כהן (kohen) comes from the unused root כהן (khn). Other derivations are:
- The verb כהן (kahan), which is the noun כהן (kohen) used as a verb, and thus it means to minister in a priest's office or function (Exodus 40:13, Deuteronomy 10:6).
- The feminine noun כהנה (kehunna), meaning priesthood (Exodus 29:9, Joshua 18:7).