hormone n.

"organic compound produced in animal bodies to regulate activity and behavior," 1905, from Greek hormon "that which sets in motion," present participle of horman "impel, urge on," from horme "onset, impulse," from PIE *or-sma-, from root *er- (1) "to move, set in motion." Used by Hippocrates to denote a vital principle; modern scientific meaning coined by English physiologist Ernest Henry Starling (1866-1927). Jung used horme (1915) in reference to hypothetical mental energy that drives unconscious activities and instincts. Related: Hormones.