Charisma is probably the most misunderstood and abused of D&D's six ability scores. When I was a younger man, Charima was widely misunderstood to be a synonym for "physical attractiveness," a claim belied by Unearthed Arcana's later introduction of a seventh ability score, Comeliness. To be fair, this misunderstanding was widespread and abetted to varying degrees by various D&D products, such Deities & Demigods, where very high or very low Charisma scores inspired worship and fear respectively, not to mention untold numbers of beautiful or handsome NPCs who possessed concomitantly high Charisma scores. Later, as the importance of henchmen and hirelings was downplayed, Charisma came increasingly to be viewed as a "dump stat" without much mechanical utility in the game.
Charisma is, of course, a transliteration of the Greek word χαρισμα, which means something like "gift of grace." It's an old word sometimes used in pagan contexts but that gained new life and depth of meaning when it was used by the Greek translators of the Hebrew scriptures known to history as the Septuagint. In that context, charisma came to mean "divine favor" and is usually applied to someone whom God has blessed in a unique and powerful way. This meaning was one shared by the writers of the New Testament, who, of course, were familiar with the Septuagint.
This prolog is intended to lay the groundwork for an odd thought I had today. In Greyhawk, paladins have only two requirements: they must be of Lawful alignment and they must have 17 Charisma. There are no other expectations about an OD&D paladin, in contrast to AD&D's much more strenuous ones (five out of the six ability scores have minimums). I'll admit that that sometimes seems odd to me, even though I adopted it in my Dwimmermount campaign. Of all the ability scores to have as an entry requirement, why Charisma? Why not, say, Wisdom? What exactly does Charisma represent that makes it a particularly good determinant of what character qualifies as a paladin?
That's when the notion of Charisma as divine favor struck me as a possible explanation. Now, it's not a perfect explanation by any means. There are lots of problems with it, chief being how divine favor ties into being a good leader of mercenary hirelings. On the other hand, high Charisma does make monsters less likely to attack you on sight, too, and that I can buy as a sign of godly influence. Of course, part of me then starts to wonder about how this divine favor might manifest more generally (or not). What about a character with only 15 Charisma who's not a Lawful fighter? Does he get some benefit, too, and, if so, what is it?
And that's where my train of thought derails and I decide not to think any more about this topic -- even though I know I will.