When did the expression "Poor man's [noun]" originate? Where does it come from, and who is considered responsible for coining it?
The Online Etymology Dictionary says that "poor man's something" is from 1854.
It was initially meant to reference any item in Poor Richard's Almanack. The publication appeared continually from 1732 to 1758.
In the Bible (Deut 16:3), Matzah (unleavened bread) is referred to as לחם עני, the bread of affliction as in the bread consumed by the Hebrew slaves in ancient Egypt. The word עני when vowelized as Oni means affliction but when vowelized as Ani means poverty. Hence לחם עני is also referred to as Poor man's bread. The idea that a poor man (afflicted by poverty) is forced to make do with an ersatz or poor substitute.