From ischys (G2479, strength, force). Ischyros means strong, mighty, powerful, forceful — describing physical strength, spiritual power, or divine authority. It is used of humans (the 'strong man' of Matt. 12:29), of God (Rev. 18:8 — 'the Lord God who judges her is mighty'), and as the root of ischyō (to have strength, be able).
The word ischyros appears in one of Jesus' most theologically loaded parables — the parable of the Strong Man (Matt. 12:29; Luke 11:21-22). Jesus describes Satan as a ischyros (strong man) who must be bound before his goods can be plundered. Jesus' exorcisms are the plundering of Satan's kingdom — proof that One stronger (ischyroteros) has arrived. John the Baptist uses the same comparative form: 'After me comes one who is more powerful (ischyroteros) than I' (Matt. 3:11). Paul in 1 Corinthians 1:25 delivers the great paradox: 'The weakness of God is stronger (ischyroteron) than human strength.' The cross — the ultimate display of apparent weakness — is in fact the mightiest act in history. Divine strength is not brute force but cruciform power — love that overcomes by giving itself away.