An Etymological Dictionary of Astronomy and Astrophysics

Something that incites or rouses to action; an incentive.
Physiology: Something that causes a physical response in an organism,

Etymology (EN): From L. stimulus “goad, spur;” cognate with Pers. tiz→ sharp.

Etymology (PE): Gavâz “goad, a stick with a pointed end, for driving cattle,” Mid.Pers. *gawâz, lowned in Arm. gawazan “goad;” Av. gauuāza- “whip, stick for driving cattle,” from gao- “cattle, cow” (→ Bootes)

• āza-, from az- “to drive,” azaiti “drives;” cf. Skt. aj- “to drive,” ájati “drives;” Gk. agein “to lead, guide, drive;” L. agere “to do, set in motion,” → act.