Usually said when you are happy and English cannot describe it alone. Also, when you are slightly embarressed/uncomfortable about something you could say it to yourself, or to a nearby friend who knows what the god damned hell you're on about. Add another "wuw" to reinforce the meaning.
"ric" is someone who shall not be named, and "du" originated from "nick duusch" (look it up on here for definition) whereby the du was taken as to combine the ric (someone who we don't particularly like), and du (from nick du, look it up remember) which makes it an insult.
"what bloody ric du, last night he used too many kleenex tissues"