late 14c., seintefie "to consecrate," from Old French saintefier "sanctify" (12c., Modern French sanctifier), from Late Latin sanctificare "to make holy," from sanctus "holy" (see saint, n.) + root of facere "to make" (see factitious). Form altered in English c.1400 to conform with Latin. Meaning "to render holy or legitimate by religious sanction" is from c.1400; transferred sense of "to render worthy of respect" is from c.1600. Related: Sanctified; sanctifying.