Shakespeare's Juliet once asked "what's in a name?" and I can say that for the majority of medieval (and Renaissance) poets, the answer would be: everything. Names often encapsulate a character's personality or defining quality, or possibly even his/her function in the story.
So what does this have to do with Erec and Enide, you ask? Quite a lot, I imagine. After all, how many times have you ever heard the name "Enide" in literature? I don't know about you, but I can't imagine that Chrétien just picked them out of a hat, so it occurred to me to find out what they mean.
According to several hopefully-reputable sites *cough* Erec's name comes from (you guessed it) a Scandinavian origin, and means "ever ruler." More interestingly, though, Enide's name comes from the Welsh, and means either "soul" or "life."
I don't know about you guys, but I find Enide a much more interesting and compelling character than Erec, and after we all pointed out the oddity of Enide's name not showing up until nearly the end of the story, I've been pondering it nonstop ever since. Why withhold her name? In a sense, there's no point in it--medieval manuscripts would have included the title of the work at the top, the same as we would do, so any reader with a smattering of brains could figure out which woman is Enide, at least by process of elimination.
One of the possibilities I thought of had to do with an independent study I did last semester. I studied a gigantic piece of Renaissance allegorical poetry known as the Faerie Queene by Edmund Spenser. Throughout the chunks of it I read, Spenser often did this interesting thing where he would only give the name of the character once he'd finished the "portrait" of the character, so often you wouldn't know a character's name until the end of their scene in the book, if not later. In the same way, I think it's possible Chrétien wanted to hold out on Enide's name until her portrait was done--meaning, once she'd matured and changed, and the reader had a chance to get a real feel for her character. Maybe, too, he didn't feel that she fully embodied her name until that point, whereas Erec always displays the pomposity/imperiousness that fully suits the meaning of his name.
So, in essence, my question is (drumroll please): why does Chrétien/the narrator choose to reveal Enide's name when he does? I know this question seems a little frivolous and perhaps slightly unimportant, but I think it's these small details that can really reveal a lot. Plus I'm just curious, so speculate (intelligently) away.