Stemming from the scottish word shelag (an extremly dope young female and/or farm animal) Shelagged means that you had kinky sex with a hot girl. So if you shelagged someone had you pretty much are the freakin man!
Usually referring to an online video that is set up. An alternative of fake or staged. First used by mistake on wtfpeople.com by nuII. It was then reused by another member VipeNero to humiliate him. Since then it has become a word in itself.