"bachatchya"  How to pronounce and the meaning? 
When did this start to be used?

Isn't it just "back at ya" pronounced "back-at-cha". With meanings
along the lines of 'the same to you'.

Spanky

Thank you !That must be it! 
Why didn't I see that!
 Do you know when it started being used on the internet? 
 I saw it for the first time today?

Well I don't know if it is actually a very common internet saying, I
don't think I've ever heard it before today. Searching Google for
"bachatchya" only turns up 7 results:
://www.google.com/search?q=bachatchya&hl=en&lr=&safe=off&filter=0

However, searching for "backatchya" turns up 1120 results so I'm
guessing that 'bachatchya' is actually a mis-spelling of 'backatchya'.
As far as how long 'backatchya' has been used online, I found
references to it as early as 2000 on the first search results page
although I have no doubt that its first utterence occured many years
before since its an internet version of a real-world saying which has
existed for God knows how long whereas internet sayings such as 'lol'
evolved from the Internet itself and so are probably younger!

Glad I could help! :-)


Spanky