To summon up strength to bear pain, misfortune, or some other unpleasant matter, or determination for a difficult task. The idea of setting one’s teeth goes back to the ancient Greeks and Romans. Menander wrote, “Set your teeth and endure” (The Girl from Samos, ca. 300 b.c.). “Gritting the teeth” describes both setting or clamping them together and grinding them with the effort. In 1797 Thomas Jefferson described his colleague, “Mr. Adams . . . gritting his teeth, said . . .”