mid-14c., from O.Fr. blasfemer "to blaspheme" (14c., Mod.Fr. blasphémer), from L. blasphemare (in L.L. also "revile, reproach;" cf.
blame), from Gk. blasphemein "to speak lightly or amiss of sacred things, to slander," from blasphemos "evil-speaking" (see
blasphemy).