The connotation of "proletariat"

In 2003, I asked Al Kelly, at the time the Edgar B. Graves Professor of History at Hamilton College, the following question. He replied as follows.

Q: In The Death of Nature, Carolyn Merchant refers to the “lower orders of society.” Is the proletariat synonymous with these “lower orders,” or does the proletariat carry specifically Marxist connotations?

A: Proletariat usually refers to modern industrial workers. Most in the lower orders of society in the 17th century were peasants.