mid-14c., "deserving of or exciting suspicion," from Old French sospecious, from Latin suspiciosus, suspitiosus "exciting suspicion, causing mistrust," also "full of suspicion, ready to suspect," from stem of suspicere "look up at" (see suspect (adj.)). Meaning "full of suspicion, inclined to suspect" in English is attested from c. 1400. Poe (c. 1845) proposed suspectful to take one of the two conflicting senses. Related: suspiciously; suspiciousness.
