He's good people. Just him. The one guy

The New Partridge Dictionary of Slang and Unconventional English (2008) says:

good people noun a person who can be trusted and counted on US, 1891

Via the American Dialect Society mailing list are these 1894 and 1891 citations:

On Tue, Nov 07, 2006 at 02:09:40PM -0500, Benjamin Zimmer wrote:

Jonathon Green previously found "good people" (used for an individual) back to 1896:

http://listserv.linguistlist.org/cgi-bin/wa?A2=ind0405c&L=ads-l&P=3773

Here it is in an 1894 list of New York slang terms in the Milwaukee Journal ("Street Slang Up To Date," reprinted from the New York World):

---

1894 Milwaukee Journal 10 Feb. 6/4 "Good people" is a universal expression applied alike to an individual and a company. It means a good fellow or a crowd of good fellows. [19th C. US Newspapers]

Note that OED subsumes this under people 2.d., which has an 1891 example (from Maitland) of "He is great people".

Jesse Sheidlower

This is an example of synecdoche. Here's some other of the same type from Wikipedia:

A general class name used to denote a specific member of that or an associated class

• "the good book," or "The Book" for the Bible ("Bible" itself comes from the Greek for "book")
• "truck" for any four-wheel drive vehicle (as well as long-haul trailers, etc.)
• "He's good people." (Here, the word "people" is used to denote a specific instance of people, i.e., a person. So the sentence would be interpreted as "He's a good person.")

NGrams certainly corroborates the usage:

Strangely, "he is good people" is completely unheard of. Even looking at "he is good people" on its own graph draws a blank.

As for anecdotal evidence, I consider myself Midwestern and do not consider this an accepted phrase. If I heard it I would assume that the speaker was messing around intentionally.

Googling around for an origin reveals plenty of people asking about it with tales ranging across America. There seems to be some consensus that the phrase is more common in the Midwest or South and random guesses involving various classes (i.e. ghetto, rural).

Two online dictionaries have included the term "good people" specifically to refer to this usage:

(slang) A good person. (Wiktionary)

(slang) A good person. (Wordnik)

I don't really consider either of these very good sources, however. Most other dictionaries that included the term "good people" used this definition:

Good folk, or Good people, fairies; brownies; pixies, etc. [Colloq. Eng. & Scot.] (Free Dictionary — chosen for its completeness; see also Dictionary.com)

Without a more specific origin, I can imagine a few ways that this phrase was created. The most obvious is changing "they are good people" to work with a single person but keeping the words "good people" for one reason or another. I doubt that it specifically links back to meaning "fairies". My hunch is that the plurality was simply confused with that of similar terms:

They are white collar / He's white collar

They are southern / He's southern

They are CS / He's CS

They are good people / He's good people

But this is pure speculation. I find the non-existence of "he is good people" in NGrams a good tip against this theory. Straight Google searches show that some people do use that phrase — apparently none of them have been scanned into NGrams.

In any case, the internet's consensus is that "he's good people" is ungrammatical. One should use one of the following in substitute:

• he's a good person
• he's good
• he's one of the good people