How Well Do You Know English Slang?
1866, shortening of professional (n.). The adjective is first recorded 1915 (in golfing's pro shop).
"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 abbr. proline
: pro ranks
[the last sense perhaps fr professional reinforced by prostitute, or vice versa]
A prophylactic for preventing venereal disease; condom; rubber (WWII armed forces)