An Etymological Dictionary of the German Language/Jahr
Jahr, n., ‘year,’ from the equiv. MidHG. and OHG. jâr, n.; a common Teut. term; comp. Goth. jêr, OIc. ár, AS. geâr, E. year, Du. jaar, OSax. jâr (gêr), n., ‘year.’ The orig. meaning of the word, which also appears in heuer, seems to be ‘spring,’ as is indicated by the Slav. cognate jarŭ, ‘spring’; comp. also Gr. ὥρα, ‘season, spring, year,’ and ὥρος, ‘year,’ so too Zend yâre, ‘year’; in Ind. a similar term is wanting (comp. Sommer and Winter). For the change of meaning see the history of the word Winter.