Use of the word "all"

I thought it was P.T. Barnum…

I believe his famous quote is, “There’s a sucker born every minute.”

I thought “all” is what they put in cars.

No. They put “erl” in cars.

When speaking to a group, y’all is general (I know y’all)as in that group of people is familiar to you and you know them as a whole, whereas all y’all is much more specific and means you know each and every person in that group, not as a whole, but individually (“I know all y’all.”) Y’all can also be used with the standard “'s” possessive.

Y’all is distinctly separate from the singular ‘you’. The statement, “I gave y’all my payment last week,” is more precise than “I gave ‘you’ my payment last week.” ‘You’ (if interpreted as singular) could imply the payment was given directly to the person being spoken to when that may not be the case.

The Chattanoogan.com; Patricia’s Porch Talk: In Plain, Southern English
by Patricia Paris (an exerpt)
posted October 2, 2006

Lynn, thanks for an “institutional” confirmation of the understanding I related above.

What this adds that I didn’t mention is that “y’all” can refer to an “impersonal” entity including more than one person (such as a company, in this example). Though company is singular, it includes more than one person–an implied plural, like a collective noun.

The second citation is a good example that “all y’all” is used for emphasis (“each and every person in that group…individually”).

i dunno what all’a yinz’re all talkin about.

an’nat.