An Etymological Dictionary of the German Language/bis
bis, conj., adv., ‘until, as far as,’ from MidHG. biȥ (for which unze, unz most frequently occur); in OHG. it was perhaps biaȥ, i.e. bis is a compound of bĭ (see bei, Goth. bĭ) and aȥ (OHG. aȥ, ‘to,’ Goth. at, Lat. ad); biaȥ became biȥ, ‘until’ Earlier ModHG. has a variant bitze, bitz, which likewise arose from an older bi and ze, ‘to.’ Similarly ModHG. unz is composed of unt (Goth. und) and ze. —