Is it ensure, insure, or assure?
late 14c., from Middle French suffocation, from Latin suffocationem (nominative suffocatio) "a choking, stifling," from past participle stem of suffocare "suffocate," originally "to narrow up," from sub "up (from under)" (see sub-) + fauces (plural) "throat, narrow entrance."
suffocate suf·fo·cate (sŭf'ə-kāt')
v. suf·fo·cat·ed, suf·fo·cat·ing, suf·fo·cates
To impair the respiration of; asphyxiate.
To suffer from lack of oxygen; to be unable to breathe.