It is found in many English words related to poison, such as:
* Toxic: Poisonous, harmful.
* Toxicology: The study of poisons and their effects.
* Antitoxin: A substance that counteracts a poison.
* Toxemia: Poisoning of the blood.
* Toxoplasmosis: A parasitic infection caused by a protozoan called Toxoplasma gondii.
So, whenever you see "tox" in a word, it's a good indication that the word has something to do with poison.