An Etymological Dictionary of the German Language/ein
ein, num., from the equiv. MidHG. and OHG. ein, ‘one,’ also the indef. art. even in OHG. and MidHG.; comp. OSax. én, Du. een, AS. ân (E. one, as a num. a, an, as indef. art.), OIc. einn, Goth. ains. The num. common to Teut. for ‘one,’ orig. ainos, which is primit. cognate with Lat. ûnus (comp. commûnis and gemein, ‘common’), and also with OIr. óen, OSlov. inŭ, Lith. vënas, Pruss. ains, ‘one.’ From this old num., which strangely enough is unknown to East Aryan (in which the cognate terms Sans. êka, Zend aéva, ‘one,’ occur), Gr. (dial.) has preserved οἰνός, ‘one,’ and οἴνη, ‘the one on dice, ace.’ See Eiland, Einöde. —
ein, adv., ‘in, into,’ from MidHG. and OHG. în, adv., ‘in, into,’ beside which MidHG. and OHG. in with the same meaning. The long form was derived from the short, as is proved by the connection with the cognates of in, which see.