An Etymological Dictionary of the German Language/Annotated/seit

by Friedrich Kluge

seit, preposition and conjunction, ‘since,’ from Middle High German sît, preposition and conjunction, ‘since,’ adverb, ‘since then,’ Old High German sîd, adverb, ‘since then, later,’ conjunction ‘since, as, because,’ preposition ‘since.’ Compare Old Saxon sîð (also sîðor), ‘later, afterwards, since then, if’; originally a comparative adverb; compare Gothic þanaseiþs, ‘further,’ allied to seiþus, ‘late.’ As new equivalent compars. compare also Old Saxon sîð-or, Old High German sī̆dôr, Middle High German sī̆der. Middle High German sint, a variant of sît, is implied by sintemal; English since is based on Middle English sithens, sithen, Anglo-Saxon sîððân.