I am under the impression that it is a common disbelief due to the similarity between the prn of Helena and Eleanor in England. E.G. Withycombe (1976) quotes the use of both Helen and Elinor for the same person as late as 1604 in Yorkshire.
The first bearer of the name was Eleanor of Aquitaine who we can see through the original langue d'oc spelling Alienor was named after her mother Aenor. I haven't yet found anything out about the name Aenor but it doesn't look related to Helen.