An Etymological Dictionary of the German Language/gewöhnen
gewöhnen, vb., ‘to accustom, inure, habituate,’ from the equiv. MidHG. gewęnen, OHG. giwęnnan (pret. giwenita); corresponding to Du. gewennen, AS. gewęnnan, OIc. venja, Goth. wanjan, ‘to accustom’; derived from an old adj. or rather partic. wana-, ‘accustomed’ (OIc. vanr); for this word a parallel form was chiefly used, the latest derivative of which is gewohnt, ‘accustomed,’ OHG. giwon, MidHG. gewon, whence, with a dental suffix (see Mond and Habicht), ModHG. gewohnt (yet without t, Gewohnheit and gewöhnlich); allied to OHG. giwona, MidHG. gewone (gewan), ‘custom.’ For details see wohnen.