The word was originated from nexon where those programmer couldn't spell properly. In the game maplestory when a person quits the guild a message will appear saying "____ have quitted the guild."

As a result this have affected millions of people world wide into thinking that quitted is actually a word.

A word used by foreign kids that play online games, meaning quit.

The same kids also misspell by saying "quite".

Past tense of quit. A cooler way of saying quit.