poto-, pot- +
2. Etymology: Via French from Italian ptomaina; from Greek ptōma, "fallen body, corpse" and Greek piptein, "to fall".
It was once thought that food poisoning was a result of bacterial toxins, but this has been rejected by scientists.
The identification of certain alkaloidal substances, or ptomaines, is of great interest to toxicologists. In 1881, the discovery of Professor Selmi as to the formation of poisonous alkaloids, which he calls ptomaïnes, in the human body after death. In 1884, these "cadaveric" alkaloids, or "ptomaines" as they have also been called. In 1891, the chemical ferments produced in the system, the albumoses or ptomaines which may exercise so disastrous an influence.
Italian ptomaina, erroneously formed by Professor Selmi of Bologna, from Greek fallen, "body, corpse". Professor Selmi's first paper in Annali di Chimica (1876), announced the body as "la potomaina o prima alcaloide dei cadaveri"; but this was partly corrected in his work of 1878 to ptomaina. It is to be regretted that the full correction to ptomatine was not made at its reception into English.
2. Not safe for, or not fit for, drinking: The water from the stream is unpotable and because it can contain unhealthy germs.