Is it ensure, insure, or assure?
1767, in anatomy, "of or pertaining to the sacrum, from Modern Latin sacralis. In anthropology, "pertaining to religious rites," 1882, from Latin sacrum "sacred thing, rite" (see sacred). Related: sacralization.
sacral sa·cral (sā'krəl)adj. In the region of or relating to the sacrum.