In ancient times some armies equipped their archers with poisoned arrows.
Greek and Roman writers referred to it as a practice of barbarians, and, in order to describe it, the Greeks had to distort the meanings of some of their own words.
Thus the Greek word for an archer’s bow was toxon, and accordingly that which pertained to a bow was said to be toxikos. From that connection the poison with which an arrow was smeared, thus making the arrow ready for the bow, was called toxikon.
The term was taken into Latin in the form toxicum, and in the Middle Ages this came to be a general term for poison of any kind, no longer connected in any way with the archer’s bow.
Hence, toxic now means “poisonous,” and the verb intoxicate originally meant “to poison.”