The story
From resinifera + toxin, in reference to the plant Euphorbia resinifera (resin spurge), from which it is extracted.
Etymology from Wiktionary, CC BY-SA 4.0.
resiniferatoxin
Today it means: A naturally occurring ultrapotent capsaicin analogue (having in its pure form a Scoville heat unit measure of 16,000,000,000) that activates the receptor TRPV1 (aka vanilloid receptor 1 or the capsaicin receptor) in a subpopulation of primary afferent sensory neurons involved in nociception. Full definition →