Why is it "miserere mei" but "miserere nobis"?

Latin Learning Latin
1

I’ve been listening to some sacred music tonight and in the Gloria, among other places, “miseror” is used with the dative “nibis” instead of the prescribed genitive. I was thinking that maybe that was just a medieval thing, but I remembered the hymn/psalm “Miserere mei, Deus” which would also be medieval (or at least late antiquity). “Nobis” is more idiomatic in English but I’ve looked it up in a few places and they all say that that verb takes the genitive.

Is there any rhyme or reason to this?

ed: I should have clarified that “miseror” means “to have mercy”.

2

Found this.

http://latindiscussion.com/forum/latin/miserere-nostri-vs-miserere-nobis.16907/

3

Interesting. Thanks.

4

It looks like the only example of misereri with a dative during Classical times is in the Fabellae of C. Julius Hyginus (~10BC). But this is considered a very inept piece of work probably by a teenager, so it could well be an error. This is according to Lewis and Short, but I’m not positive so let me know if you know any other Classical examples.