Neo-Con is short for Neo-Conservative, and origianally refered to many ex-Democrats who joined the conservative movement in the 1970s to 1990s, brining with them their idea of a large federal government, which 'classic' conservatives opposed.
Chicken-hawk is a play on words. Someone who is supposedly in favor of war (called "hawks") but who is actually a coward ("chicken"). Also a reference to an annoying cartoon bird of that name, from the Foghorn Leghorn cartoon.
While used mainly for name-calling and ad hominem attacks, it is better than most comparable terms because it actually has a coherent meaning, and some people could accurately be described by that term. However, as with most terms, it usually ends up being mis-applied as "anyone we don't like".