1892 (n.) "an adherent of populism," also (with capital P-), "a member of the Populist Party;" 1893 (adj.); American English, from Latin populus "people" (see people (n.)) + -ist. Originally in reference to the U.S. Populist Party (or People's Party), organized February 1892 to promote certain issues important to farmers and workers (expansion of the currency, state control of railways, and restriction on the ownership of land). The term outlasted the party, and by 1920s came to mean "representing the views of the masses" in a general way, and from the 1950s as "anti-establishment" on either the left or the right.
