Is it ensure, insure, or assure?
early 15c., "barren" (implied in sterility), from Middle French stérile "not producing fruit," from Latin sterilis "barren, unproductive," from PIE *ster- "sterile, barren" originally "stiff, rigid" (cf. Greek steresthai "be deprived of," steira "sterile," stereos "firm, solid, stiff, hard;" Sanskrit starih "a barren cow;" Old Church Slavonic sterica "a barren cow;" Gothic stairo "barren;" Old Norse stirtla "a barren cow"). See torpor. Originally in English with reference to soil; of females, from 1530s. The sense of "sterilized" is first recorded 1877.
sterile ster·ile (stěr'əl, -īl')
Not producing or incapable of producing offspring.
Free from all live bacteria or other microorganisms and their spores.