means A poisonous substance produced by a living organism — a plant, animal, or microbe — capable of causing harm or death in another creature.

from From Greek 'toxikon,' meaning 'poison for arrows' — itself from 'toxon,' a bow. The full phrase was 'toxikon pharmakon,' the drug smeared on arrowheads, and over time the deadly smear swallowed the weapon's name. So buried inside 'toxin' is an archer drawing a bow, the poison and the projectile fused into one word.