Douglas Harper's Etymology Dictionary
by 1879, U.S. dialect abbreviation of you all (see you, and compare yins).\n\nChildren learn from the slaves some odd phrases ... as ... will you all do this? for, will one of you do this?
["Arthur Singleton" (Henry C. Knight), "Letters from the South and West," 1824]
\nWe-all for "us" is attested by 1865; we-uns by 1864. Who-all attested from 1899.Wiktionary
pron. (context chiefly US dialect Southern US English) (non-gloss definition plural Plural form of '''you'''.)
Wikipedia
Y'all (sometimes yall or ya'll) is a contraction of you and all (sometimes combined as you-all). It is used as a second-person pronoun. The exclusive usage of y'all as a plural pronoun is a subject of perennial discussion. Y'all is strongly associated with Southern American English, and appears in other English varieties, including African American Vernacular English and South African Indian English.
Y'all magazine is an American magazine based out of Oxford, Mississippi, literary hub of the American South. It was published bimonthly with a circulation of 100,000 and features Southern celebrities, events and ordinary people with extraordinary stories to tell. According to the magazine's mySpace page, "Y'all covers the South's 15 states and its 103 million people, just like kudzu."
Y'all were James Dean Jay Byrd and Steven Cheslik-DeMeyer, a neo-vaudeville country folk duo founded in New York in 1992. Their act incorporated original songs with stories based on a semi-fictionalized version of their own biographies. Many of the stories centered on Byrd's "lucky green dress," which, according to the lore they created, was given to him by a cross-dressing trailer salesman uncle and which Byrd continued to wear for luck. They released several albums on audiocassette and CD, published a novelized back story, performed in theaters, on television and radio, and in rock clubs, churches, retirement homes, and folk coffeehouses all over the United States, Canada, and the UK before separating in 2002. Y'all were compared to the Everly Brothers, the Louvin Brothers, the Smothers Brothers, Garrison Keillor, Simon & Garfunkel, the Magnetic Fields, They Might Be Giants, and Sonny & Cher.
Country harmonies were in their blood. Jay grew up in East Texas, the son of a country preacher. He didn't know who the Beatles were until he was 18—only gospel music was allowed in the house. Steven grew up without the benefit of church, but his mother's love for Johnny Cash and Loretta Lynn was nearly religious. Jay also inherited his father's gift of gab, which found its foil in Steven's deadpan shyness.
Usage examples of "y'all".
Y'all are both my boyz, and I'm not trying to see either one of you iced over a woman.
Shabazz, you know I can't eat that vegetarian bird food y'all keep pushing.
Y'all been in my place on more'n one occasion, most likely, and I was jest wonderin': at any time did you happen to remove from the premisesfor your own good reasons, naturallya spoon, a little bitty silver spoon, and a colored stick?
And y'all went gaga over _her_ and couldn't even be bothered with me.
And y'all went gaga over her and couldn't even be bothered with me.