Is it ensure, insure, or assure?
c.1200, "find fault with;" c.1300, "lay blame on," from Old French blasmer (12c., Modern French blâmer) "to rebuke, reprimand, condemn, criticize," from Vulgar Latin *blastemare, from Late Latin blasphemare "revile, reproach" (see blaspheme). Replaced Old English witan with long "i." Related: Blamed; blaming.
early 13c., from Old French blasme "blame, reproach; condemnation," a back-formation from blasmer (see blame (v.)).