English, from Greek meaning either "sun's rays" [ONC] or "bright one" [Whyte].
In the 1841 Census of Aberdeenshire there are many spelling variations for Helen and Helenora. Most of these rare spellings should be found with a Soundex search.
A discussion on a Ireland (Cork) exchange site has identified a number of variations in the Gaelic form of Helen. These include Aibhilin, Aibhlin, Eibhlinn, Eilidh, Léan and Léana.
In old documents Helena was used for Helen, Ellen, Ellyn and Elinor, with appropriate Latin endings.
A correspondent [TG2] reports that "... in the Census records of Strathdon, Scotland, the spelling variation Hellen seems to be common".