A commenter provides the following:
Back to the subject at hand: One of my own pet peeves is the use of “insure” where the writer clearly means “ensure”. “Affect” for “effect” is just as bad, but not nearly as common; these days, it seems like everybody and his dog misuses “insure”. I’d check a dictionary or style manual for support, but I’m worried that the new usage of “insure” has become so common that they may consider it correct.
Oh, buddy, it’s worse than you can imagine. Much worse. From the Oxford English Dictionary definition of “insure” (definition 5 is the modern one, but I include #1 because of the back-reference to it in #5):
1. trans. To make (a person) sure (of a thing); to give security to (a person) for the fulfilment of something: cf. ASSURE v. 9, ENSURE v. 1, 2. Obs.
c1440 Promp. Parv. 262/2 Insuryn, or make suere, assecuro. 1681-6 J. SCOTT Chr. Life (1747) III. 21 Thus Christ..hath taken the most effectual Care to insure the mutual Performance of this everlasting Covenant to both Parties..to insure God of our performing our Part..and to insure us of God’s performing his Part….
5. trans. To make certain, to secure, to guarantee (some thing, event, etc.): = ASSURE v. 5, 7a, ENSURE v. 8, 9.
1681-6 [see sense 1]. 1809 W. IRVING Knickerb. VII. xiii. (1849) 450 Such supineness insures the very evil from which it shrinks. 1821 MRS. SHERWOOD Hist. Geo. Desmond 19 He had insured for me the situation of a writer on the Bengal establishment. 1849 RUSKIN Sev. Lamps vi.