Is it ensure, insure, or assure?
1540s, earlier sinthoma (late 14c.), from Medieval Latin sinthoma "symptom of a disease," from Late Latin symptoma, from Greek symptoma (genitive symptomatos) "a happening, accident, disease," from stem of sympiptein "to befall," from syn- "together" (see syn-) + piptein "to fall," from PIE *pi-pt-, reduplicated form of root *pet- "to rush; to fly" (see petition (n.)). Spelling altered in English by influence of Middle French and Late Latin forms. Symptomatic in general sense of "indicative (of)" is from 1751.
symptom symp·tom (sĭm'təm, sĭmp'-)
An indication of disorder or disease, especially when experienced by an individual as a change from normal function, sensation, or appearance. Also called sign.
A subjective indication of a disorder or disease, such as pain, nausea or weakness. Symptoms may be accompanied by objective signs of disease such as abnormal laboratory test results or findings during a physical examination. Compare sign.