I am working with the 1850 census of Tuscaloosa County, Alabama, right now, and Ellender is turning up frequently there, too.
I doubt if it has anything to do with
Eluned. It is probably a variation of
Eleanor created partly by example from
Alexander, and partly because "d" is often "intrusive" in English after "n". For example, the Old English words
dwinan and
thunor became the Middle English words
dwindle and
thunder.