Urban dictionary has an entry for Try Harding meaning something like “a person who tries too hard to get girls but is always unsuccessful.”
On the right column of that entry has a list of “TryHard” words. It does sound like it is from gaming but has leaked over into other senses.
Or the UD entry for Try Hard as a word.
A person who puts a large amount of effort into achieving a certain image, or counter-image, to the point where it is obviously contrived. Rather than achieving an image through genuine personality, the try-hard consciously attempts to fit a certain style through deliberate imitation, forced style, or scripted behavior. That is to say, he/she is trying hard to create an image.
edit: a second definition suggesting that it might originate in gaming
In online video games, it is that guy who is giving it 110% all the time because winning and/or having a high kill/death ratio is more important than just having fun. Try hards are most common in games like Halo or Call of Duty and are frequently seen yelling at their teammates for dying a lot.