con (adj.)

"swindling," 1889 (in con man), American English, from confidence man (1849), from the many scams in which the victim is induced to hand over money as a token of confidence. Confidence with a sense of "assurance based on insufficient grounds" dates from 1590s.

con (n.1, adv.)

"negation; in the negative; the arguments, arguers, or voters against a proposal" (mainly in pro and con), 1570s, short for Latin contra "against" (see contra). Compare pro (n.2).

con (n.2)

a slang or colloquial shortening of various nouns beginning in con-, such as, from the 19th century, confidant, conundrum, conformist, convict, contract, and from the 20th century, conductor, conservative.

con (v.1)

"to guide a ship, give orders for the steering of a ship," 1620s, from French conduire "to conduct, lead, guide" (10c.), from Latin conducere  "to lead or bring together, contribute, serve," from com "with, together" (see com-) + ducere "to lead," from PIE root *deuk- "to lead." As a noun, "action or post of steering a ship," 1825. Related: Conned; conning. Conning tower "dome-shaped pilot house of an ironclad warship or submarine" is attested from 1865.

con (v.2)

"to swindle," 1896, from con (adj.). Related: Conned; conning.

con (v.3)

"to study, get to know, peruse carefully," c. 1200, cunnen, "make an attempt, try or seek to do," from Old English cunnian "to know" (see can (v.1)). Related: Conned; conning.