A Grammatical Dictionary of Botanical Latin

Anthrax,-acis (s.m.III), abl. sg. anthrace, charcoal, coal = L. carbo,-onis (s.m.III), q.v.; also “a precious stone of dark-red color, including the carbuncle, ruby and garnet; hence, carbuncle, malignant pustule (according to some, small-pox) (Liddell & Scott); (classical) natural cinnabar (the color of which is like a burning coal); (medicine) a virulent ulcer (in pure Lat. carbunculus) (Lewis & Short); see carbunculus,-i (s.m.II), pustula,-ae (s.f.I), ulcer [> Gk. anthrax,-akos (s.m.III), coal or charcoal]; see charcoal; see coal.

Anthrax,-acis (s.m.III), an infection caused by the bacterium Bacillus anthracis, the most common form being cutaneous anthrax, “in which large, (charcoal-)black-colored skin lesions are formed” (Wikipedia 2017).

Bacillus anthracis, Bacillus of Anthrax; bacillus, ‘small rod’ + gen.sg. anthrax, from the charcoal black skin lesions of the disease.