1550s, "one who engages in mental speculation," from Latin speculator "a looker-out, spy, scout, explorer; investigator, examiner," agent noun from speculari (see speculation). The financial sense is from 1778. Formerly also "observer, onlooker," especially "an occult seer" (1650s). Fem. form speculatrix attested from 1610s. Related: Speculatory.