Is "Marco Polo" slang?

I have heard some people utter "Marco Polo" in distress or shocking cases. Is it slang? Or is it used as something else?
Can someone great as Marco Polo be used as an abusive word?

Answer

No, to my knowledge it is neither slang as such nor offensive in any way. One possibility is that Marco Polo is being used as a substitute for Motherfu..er. The rhythm is similar and Marco is close enough to Mother to give it a nice alliterative ring.

I have never heard it used this way and it is definitely neither offensive nor vulgar. However, if you have heard people use it as an expletive, they are probably using it because it is an alliteration of the other word. Think of it as an equivalent to words like darn or drat replacing damn.