I understand this name might not be for everyone due to the association with poison, but that darker association is part of why I like it. Honestly, I'd probably choose it for myself. If you don't want to give it to a person, perhaps a black cat... or is that too cheesy?
The Italian noun “Belladonna” (deadly nightshade) likely derives originally from the Latin noun “blādōna” (mullein), actually being reanalyzed as, rather than taken directly from, a compound of “bella” (beautiful) and “donna” (woman) (also note the fact that Italian adjectives come after their noun). This pervasive folk etymology probably came from the plant’s use in cosmetics for the paling of one’s skin and especially the dilation of one’s pupils, which were both seen as hallmarks of European attraction and femininity. [noted -ed]