An Etymological Dictionary of the German Language/zu
zu, prep., ‘to, in addition to, at, in order to’; adv., ‘to, towards,’ from the equiv. MidHG. zuo (MidG. zû), OHG. zuo, zua, zô; comp. the corresponding OSax. tô, Du. toe, OFris. tô, AS. tô, E. to; wanting in OIc. and Goth. (for which Scand. til and Goth. du occur). It corresponds in non-Teut. to Lith. da-, OIr. do, as well as to Zend -da, Gr. -δε, and Lat. -do, which are used enclitically.