early 15c., "marked out, indicated" (a sense now obsolete), from Latin designatus, past participle of designare "mark out, devise, choose, designate, appoint," from de "out" (see de-) + signare "to mark," from signum "identifying mark, sign" (see sign (n.)). Meaning "appointed or nominated but not yet installed" is from 1640s.
1791, "appoint or select for a particular purpose," from designate (adj.) or else a back-formation from designation, or formed from Latin designatus. Meaning "to mark out or indicate" is from 1801; that of "distinguish from others by a name, give a name to" is by 1818. Related: Designated; designating.