According to Merriam-Webster, "you all" is very clearly related to "y'all" [1][2] [1] http://www.merriam-webster.com/dictionary/y'all http://www.merriam-webste

According to Merriam-Webster, "you all" is very clearly related to "y'all" [1][2] [1] http://www.merriam-webster.com/dictionary/y'all http://www.merriam-webster.com/dictionary/y'all [2] http://en.wiktionary.org/wiki/you_all http://en.wiktionary.org/wiki/you_all