Is it ensure, insure, or assure?
1610s, from Latin uterus "womb, belly" (plural uteri), from PIE root *udero- "abdomen, womb, stomach" (cf. Sanskrit udaram "belly," Greek hystera "womb," Lithuanian vederas "sausage, intestines, stomach, lower abdomen," Old Church Slavonic vedro "bucket, barrel," Russian vedro), perhaps originally in PIE "outer, sticking out," shifting to "belly" via "protruding."
uterus u·ter·us (yōō'tər-əs)
n. pl. u·ter·us·es or u·ter·i (yōō'tə-rī')
A hollow muscular organ consisting of a body, fundus, isthmus, and cervix located in the pelvic cavity of female mammals, in which the fertilized egg implants and develops into the fetus. Also called metra, womb.
Plural uteri (y'tə-rī') or uteruses
The hollow, muscular organ of female mammals in which the embryo develops. In most mammals the uterus is divided into two saclike parts, whereas in primates it is a single structure. It lies between the bladder and rectum and is attached to the vagina and the fallopian tubes. During the menstrual cycle (estrus), the lining of the uterus (endometrium) undergoes changes that permit the implantation of a fertilized egg. Also called womb. See more at menstrual cycle.