An Etymological Dictionary of the German Language/Abseite

by Friedrich Kluge

Abseite, f., ‘wing, aisle,’ from MidHG. apsîte, f., ‘the domed recess of a church,’ a corruption of MidLat. and OHG. absida (Gr. ἀψίς), ‘vault,’ due to its supposed connection with sîte, ‘side.’