Presumably a merger between
Jane, or
Jayne, and
Cornelia.
Jane is quietly lovely and
Cornelia is a bit fussy for me but certainly a good name. But both of them do much better as stand-alones. I really cannot warm up to Jaynelia at all. I know someone who named her daughter Nelia;
Cornelia was a family name but that person was always known as Nelia. I liked it, rather to my own surprise! Less is more, perhaps? And Jaynelia is too much more.