Preparation, readiness, or a firm foundation. Used only once in the New Testament (Ephesians 6:15), where it describes the 'readiness' that comes from the gospel of peace — part of the armor of God. The word implies being prepared and established on solid ground.
Hetoimasia in Ephesians 6:15 is the readiness of gospel-prepared feet. The Roman soldier's caligae (hobnailed sandals) gave firm footing for battle — hetoimasia is the spiritual equivalent. Believers stand firm not through their own preparation but through the gospel of peace already received. It suggests both stability (firm footing) and mobility (readiness to move with the gospel).