Great article at SEA documenting this:
Of course, the earliest Christian writers prior to Augustine (the ante-Nicene fathers) rejected all of the basic features of what is now known as Calvinism (e.g. exhaustive determinism, inevitable perseverance, limited atonement, unconditional election and predestination, etc.), while affirming the central features of what would later come to be known as Arminianism (e.g. libertarian free will, resistible grace, conditional election, the possibility and reality of true believers abandoning the faith, unlimited atonement, etc.).