The "social" in the phrase is the tell: it refers to distributive justice meted out on the basis of group membership rather than procedural justice employed on the basis of one's own behavior.
Although it was not coined by him, it was popularized by the notorious radio personality, Father Coughlin.
Thanks, that’s a helpful distinction. I would’ve guessed it was a ‘60s-vintage term, but it sounds like it goes back further than that.