However, sporadic place-name attestations demonstrate the presence of the secondary umlaut already for the early 9th century, which makes it likely that all types of umlaut were indeed already present in Old High German, even if they were not indicated in the spelling. Presumably, they arose already in the early 8th century. Ottar Grønvik, also in view of spellings of the type "ei", "ui", and "oi" in the early attestations, affirms the old epenthesis theory, which views the origin of the umlaut vowels in the insertion of after back vowels, not only in West, but also in North Germanic.