Is it ensure, insure, or assure?
c.1400 (adjective and noun), from Old French diuretique, from Late Latin diureticus, from Greek diouretikos "prompting urine," from diourein "urinate," from dia "through" (see dia-) + ourein "urinate," from ouron (see urine).
diuretic di·u·ret·ic (dī'ə-rět'ĭk)adj. Tending to increase the discharge of urine. n. A substance or drug that tends to increase the discharge of urine.
A substance that increases the rate of urine production.