The phrase "supply creates its own demand" was used in 1860

Google Ngrams says the phrase can be found in 1843... Maybe in 1845.

Here's the image. (The image says zero smoothing but appears to show smoothing 3. At smoothing zero there is a short spike at 1845.)

Here's the site.

The earliest reference they turn up is from 1860. 

 

 

From 1860: The Covenanter, page 304

The first use of the phrase "supply creates its own demand" was in reference to grog-shops? Wouldn't that be just perfect!!

This one is attributed by Google Books to 1886. If that was correct, this find would be a big deal. Keynes wouldn't have written it: he was born in 1883.

Here's the search result:

No, but it uses the phrase "tacitly assuming". It's probably Keynes. 

It is Keynes. Brad DeLong provides the evidence:

Here's the snippet, for what it's worth:

The whole of item (2) may be found on the last page of the PDF at DeLong's site.

 From 1897: Imperial Fresno, page 110 

"The market for good dried figs is unlimited".