Free market is an evolution of the concept laissez-faire market after early economists realised that leaving market participants to do their own thing didn't ensure a competitive market.

There'd always been a belief in early capitalists that an unregulated market would be inherently self-regulating from competition, in a way that allowed for competition, and yeah, well, I would emphasise the word "belief" in that.

I once met a theologian who had done their PhD on the language used by a politically powerful neoliberal group in their writings on the market and came to the conclusion that it was primarily the language of faith, not the language of science.