An Etymological Dictionary of the German Language/Zitteroch
Zitteroch, m., ‘herpetic eruption,’ from the equiv. MidHG. ziteroch, OHG. zittaroh (hh), m. (ttr remains unpermutated as in zittern); corresponding to AS. tëter, E. tetter, to tetter. Allied in the non-Teut. languages to Sans. dadru, dadruka, ‘cutaneous eruption,’ Lith. dedervine, ‘tether, scab,’ and Lat. derbiosus (from derdviosus?). AS. tëter is based like Sans. dadru on an Aryan de-dru-, a reduplicated form (like Biber); OHG. zittaroh is borrowed from it.