From apo (from) + lytrōsis (ransoming) — a release effected by payment of a ransom. In the ancient world, it described buying a slave's freedom. The NT applies it to Christ's work: He paid the ultimate price to liberate humanity from sin, death, and bondage.
Apolytrōsis is marketplace language applied to salvation — God purchased our freedom at the cost of His Son's blood. 'In him we have redemption through his blood' (Ephesians 1:7). The word has three tenses in the NT: past (we have been redeemed), present (the Spirit is a deposit guaranteeing redemption), and future (the redemption of our bodies at Christ's return, Romans 8:23). Freedom is bought, not earned.