Is it ensure, insure, or assure?
c.1400, from Late Latin syncopen "contraction of a word," accusative of syncope, from Greek synkope, "contraction of a word," originally "a cutting off," from synkoptein "to cut up," from syn- "together, thoroughly" (see syn-) + koptein "to cut," from PIE root *kop- "to beat, strike" (see hatchet). In pathology, "failure of the heart's action," hence "unconsciousness."
syncopic syn·cop·ic (sĭn-kŏp'ĭk)
syncope syn·co·pe (sĭng'kə-pē, sĭn'-)
A brief loss of consciousness caused by a sudden fall of blood pressure or failure of the cardiac systole, resulting in cerebral anemia.