suspect (adj.)
early 14c., "suspected of wrongdoing, under suspicion;" mid-14c., "regarded with mistrust, liable to arouse suspicion," from Old French suspect (14c.), from Latin suspectus "suspected, regarded with suspicion or mistrust," past participle of suspicere "look up at, look upward," figuratively "look up to, admire, respect;" also "look at secretly, look askance at," hence, figuratively, "mistrust, regard with suspicion," from assimilated form of sub "up to" (see sub-) + specere "to look at" (see scope (n.1)). The notion behind the word is "look at secretly," hence, "look at distrustfully."
suspect (n.)
"a suspected person," 1590s, from suspect (adj.). Earlier as a noun it meant "a suspicion, mistrust" (late 14c.).
suspect (v.)
mid-15c. (implied in suspected), from suspect (adj.) and in part from Middle French suspecter or directly from Latin suspectare "to mistrust," frequentative of suspicere. Related: Suspecting.