mou' or 'st'arxidia mou' (pronounced, star-he-dee-a-moo) is a popular modern Greek saying that directly translates: "to my testicles" but refers to writing something you don't care about on your testicles. It roughly means I don't care, or I don't give a shit.
Someone: Hey I just saved a bunch of money on my car insurance!
You: St'arxidia mou!
Someone: If you do that you will get into trouble!
You: St'arxidia mou! Did I ask you?