Maybe it will help you... http://www.italki.com/knowledge/page/Phrasal%20Verb%20-%20Get%208%20verbs%20you%20should%20know!.htm

"He's a right lazy so-and-so. He's always trying to GET OFF doing any work." This is the strictly correct version. ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' "I want to GET OFF OF Friday." This I remember from 1978 at Lucas Electronics in Birmingham. The strictly correct version is with ON instead of OF. OF is used, but I don't think it's AOK. "Hey, hey, you, you, get off of my cloud." The Rolling Stones' line. Again, there it is, but I don't think you're going to pass the exam if you use it. Is it slang? I don't know. It may be best to avoid it unless you're in an informal situation e.g. with your pals.

get or knock off at work .