1610s; see insect + -vorous "eating, devouring." The mammalian class of Insectivora is from 1821; insectivore (n.) is from 1858 (both are earlier in French).
inscrutable
insect
insectarium
insecticide
insectivore
insectivorous
insecure
insecurity
inseminate
insemination
insensate