1731, from infra- + Latin lapsus "a fall" (see lapse (n.)) + ending from unitarian, etc.

[In theology], the doctrine held by Augustinians and by many Calvinists, that God planned the creation, permitted the fall, elected a chosen number, planned their redemption, and suffered the remainder to be eternally punished. The Sublapsarians believe that God did not permit but foresaw the fall, while the Supralapsarians hold that God not only permitted but decreed it. [Century Dictionary]