Very nice. I really like it. I don't like it enough to use myself, lest it be a pet name or nickname for Loretta, but I'd love for someone to use it.
Etta Catherine is spectacular, but of course, I'm biased.
Etta Frances is very nice. Very evocative of the 1920s to me.
Suggestions:
Etta Marion
Etta Felicia
Etta Rachel
Etta Leonore
Etta Sylvie
Etta Primrose
Etta Noor