Doubled with Meaningful Name: Helga means "hell/underworld girl", while Olga means "heavenly girl". Their parents were unfair from the very beginning!
This started out just saying (incorrectly) what Helga's name meant, then the line was edited with Olga's name's meaning From a Certain Point of View. Helga means, basically, "blessed", and Olga is a later and foreign version of Helga. The "Hel" in "Helga" has nothing to do with Hel or her domain, it's just an Anglicization, and "-ga" isn't even a thing, it's just an Anglicisation of the feminine name-suffix "-gr".