An Etymological Dictionary of the German Language/ich
ich, pron., ‘I,’ from the equiv. MidHG. ich, OHG. ih; corresponding to OSax. ik, Du. ik, AS. ič, E. I, Goth. ik. For the common Teut. ik, from pre-Teut. egom, comp. Lat. ego, Ger. ἐγώ, Sans. aham, OSlov. azŭ, Lith. aż. The oblique cases of this primit. nom. were formed in all the Aryan languages from a stem me-; comp. mein. The orig. meaning of ich, primit. type egom (equal to Sans. aham), cannot be fathomed.