An Etymological Dictionary of the German Language/Annotated/sieben

by Friedrich Kluge

sieben, numeral ‘seven,’ from the equivalent Middle High German siben, Old High German sibun; corresponding to Gothic sibun, Anglo-Saxon seofon, English seven, Dutch zeven, Old Saxon siƀun, ‘seven’; originally septn. Like all units, a common Aryan word; compare Sanscrit saptan, Greek ἑπτά, Latin septem, Old Slovenian sedmĭ, Old Irish secht, ‘seven.’ The t of the Aryan primary form septn- disappears in primitively Teutonic between p and n.