From oikos (house) + nomos (law/management) — household management, stewardship, administration. Oikonomia describes the management of resources entrusted to someone. Paul uses it for God's plan of salvation and for his own apostolic stewardship.
Paul speaks of the oikonomia of God's grace given to him (Ephesians 3:2) — he is a steward of the gospel, not its owner. God's grand oikonomia is His plan to unite all things in Christ (Ephesians 1:10). The concept demands accountability: stewards must be found faithful (1 Corinthians 4:2). All believers are stewards of God's grace, gifts, and resources — managers, not possessors.