Old English stedefæst "secure in position, steady, firm in its place," from stede (see stead) + fæst (see fast, adj.); similar formation in Middle Low German stedevast, Old Norse staðfastr "steadfast, firm; faithful, staunch, firm in one's mind." Of persons, in English, "unshakable, stubborn, resolute" from c.1200. Related: Steadfastly, steadfastness.