soz derives from the word "sorry" and some chav just decided to throw "hard" onto the end of it.
used to piss someone off when they try and have an argument with you or used when you have made a mistake and someone has pointed it out.
a way of apolagising but at the same time telling them someone you dont give a shit what they think, and you arent really sorry and you just wanna piss them off.
no. 1: hey chav, you have got that wrong, the germans didnt win the war you frigging idiot.