An Etymological Dictionary of the German Language/Annotated/Abseite

by Friedrich Kluge

Abseite, feminine, ‘wing, aisle,’ from Middle High German apsîte, feminine, ‘the domed recess of a church,’ a corruption of Middle Latin and Old High German absida (Greek ἀψίς), ‘vault,’ due to its supposed connection with sîte, ‘side.’