1880, from Italian ptomaina, coined by Professor Francesco Selmi of Bologna, 1878, from Greek ptoma "corpse," on notion of poison produced in decaying matter. Greek ptoma is literally "a fall, a falling," via the notion of "fallen thing, fallen body;" nominal derivative of piptein "to fall" (see symptom). Incorrectly formed, and Selmi is roundly scolded for it in OED, which says proper Greek would be *ptomatine.
ptomaine pto·maine (tō'mān', tō-mān')
A basic nitrogenous organic compound produced by bacterial putrefaction of protein.
Any of various toxic nitrogenous organic compounds produced by bacterial decomposition of protein, especially in dead animal tissue. Ptomaines are bases and are formed by removing the carboxyl group (COOH) from amino acids. They do not cause food poisoning, as was previously thought, but the term ptomaine poisoning is still used to describe food poisoning caused by bacteria.