1533, "a stretched condition," from M.Fr. tension, from L. tensionem (nom. tensio) "a stretching" (in M.L. "a struggle, contest"), from tensus, pp. of tendere "to stretch," from PIE base *ten- "stretch" (see tenet). The sense of "nervous strain" is first recorded 1763. The meaning "electromotive force" (in high-tension wires) is recorded from 1802.