con (n.1)youdaoicibaDictYouDict
"negation" (mainly in pro and con), 1570s, short for Latin contra "against" (see contra).
pro (n.2)youdaoicibaDictYouDict
"a consideration or argument in favor," c. 1400, from Latin pro (see pro-). Pro and con is attested from c. 1400, short for pro and contra "for and against" (Latin pro et contra).
pro-and-conyoudaoicibaDictYouDict
"To weigh the arguments for and against; to debate both sides of (a question or matter)", Late 17th cent. Probably partly from pro and con, and partly from pro + and + con.