User blog comment:Eðkee/Heretoga's descendent/@comment-34246601-20180527223504

It would be "heretow". But it has lived on as "heretog". So it is a bit like the word "answer"; that is a mix of "and-" + "swear", but the spellings of both words on their own have shifted since then, while the same spelling shifts did not happen to it as one word.