Phrase coined by former Yo! MTV Raps host Ed Lover. Originates from his series of videos on YouTube entitled "C'mon Son," where he highlights and gives his opinion on dumb things that happen in hip-hop culture and the world. Used whenever someone does something stupid, questionable, or just plain over-the-top. Can also be accompanied by holding up a cardboard sign with the phrase written on it.
Kanye West jumped on the stage, snatched the mic from Taylor Swift, and said some dumb shit about Beyonce having the best video of all time. The best video of all time? C'mon Son!