It's quoted, I don't say it, the author of the blog post does. I think it's because he sees borrowing as the primary cause of the expansion of the money supply.
Public economy is a reference to the economic activities controlled by the public sector, i.e. the government.

Monetarism clearly states that "inflation is caused when money is printed above the real rate of growth of the economy", which in practice is traduced in the state spending more money units than the units it receives through direct taxation.

I think that is what the screenshot implies.