Is it ensure, insure, or assure?
early 15c., from Medieval Latin aneurisma, from Greek aneurysmos "dilation," from aneurynein "to dilate," from ana- "up" (see ana-) + eurynein "widen," from eurys "broad, wide," from PIE root *were- "wide, broad" (cf. Sanskrit uruh "broad, wide").
aneurysm an·eu·rysm or an·eu·rism (ān'yə-rĭz'əm)
A localized, blood-filled dilation of a blood vessel caused by disease or weakening of the vessel wall.