An Etymological Dictionary of the German Language/Annotated/offen

by Friedrich Kluge

offen, adjective, from the equivalent Middle High German offen, Old High German offan, adjective, ‘open’; it has the same meaning in all the Teutonic languages except. Gothic, where *upans is wanting. Compare Old Icelandic openn, Anglo-Saxon and English open, Dutch open, Old Saxon opan; the adjective seems similar in form to a participle, but the primitively verb cannot be adduced. It is also doubtful whether auf, Old Saxon upp, Gothic iup, is allied, so that offen would mean literally ‘drawn up.’