KV - Whaddya and Watcha

Winston Frederick Sterzel, who calls himself SerpentZA on YouTube, is very racist, and seems to particularly hate the Chinese. He says they are very greedy and will eat anything, a bit like most people I know, including me. 

Anyway, Winston Sterzel, to prove his point, says that the first thing that the Chinese will say when they meet you is, have you eaten? I knew this was probably just a way of saying hello where it's original meaning had most kikely been lost. It's a bit like Watcha in Britain, which means, what are you doing? We don't think of this when we say Watcha, though, because it's just a kind of hello. 

'Have you eaten' is a common greeting in East Asia because they had many famines in the past, but it's original meaning has been lost too, so it's become just a way of saying hello. 

It triggered me to do research on Watcha, and I found this video about it, but I had never heard of the word Whaddya before, until I watched the video right through to the end and found out that I use this word all the time. Go figure! 

Whaddya and Watcha are very common spoken English "words" but you probably will not find them in the dictionary. What do they mean and how do you use them correctly?