An Etymological Dictionary of the German Language/Wiesel
Wiesel, m. and n., ‘weasel,’ from the equiv. MidHG. wisel, wisele, OHG. wisala, f.; corresponding to Du. wezel, wezeltje, AS. wësle (weosulœ), E. weasel, Dan. väsel. It is frequently regarded as a derivative of Wiese, linking it with the place where the animal is usually found; others, on account of the keen scent of the animal, connect its name with Lat. virus, ‘poison’ (root wī̆s, see verwesen). Both derivations are very uncertain.