Borrowing from Medieval Latin tēnesmus, from Ancient Greek τεινεσμός (teinesmós, “vain endeavor to evacuate”), from τείνω (teínō, “to stretch, to pull tight”) + -εσμός (-esmós, nominal suffix). First attested in the form tenasmon in 1450, while the form tenesmo appeared in the late 16th c., becoming the predominant spelling.