An Etymological Dictionary of the German Language/gerben
gerben, vb., ‘to tan, curry, polish,’ from MidHG. gęrwen (garwen), wk. vb., ‘to make ready, prepare. equip, dress, tan’; a deriv. of gar (see gar); OHG. gariwen (garawen), from *garwjan, ‘to make ready,’ lëdergarawo, ‘tanner.’