1850, "frenzied passion," from Latin oestrus "frenzy, gadfly," from Greek oistros "gadfly; breeze; sting; anything which makes one mad, mad impulse," perhaps from a PIE *eis- (1), forming words denoting passion (see ire). First attested 1890 with specific meaning "rut in animals, sexual heat." Earliest use in English (1690s) was for "a gadfly." Related: Estrous (1900).
)window.location='https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=byronic106@yahoo.com&lc=US&item_name=Donation+to +Help+Keep+Etymonline+Free+and+Open&no_note=0&cn=&curency_code=USD&bn=PP-DonationsBF:btn_donateCC_LG.gif:NonHosted'){kind=link}