mid-14c., from Old French presumtuex (12c.; Modern French présomptueux) and directly from Late Latin praesumptuosus, variant of praesumptiosus, from past participle stem of Latin praesumere "anticipate," in Late Latin, "assume" (see presumption). Related: Presumptuously; presumptuousness.[presumptuous etymology, presumptuous origin, 英语词源]