The Greek noun brachiōn (βραχίων) means arm, specifically the upper arm or the arm as a symbol of strength and power. It appears three times in the New Testament (Luke 1:51; John 12:38; Acts 13:17), each time in quotation from or allusion to the Old Testament where "the arm of the LORD" is a central theological concept. The arm represents strength, power, and active intervention.
The "arm of the Lord" (zeroa YHWH in Hebrew; brachiōn Kyriou in Greek) is one of Scripture's most powerful images of divine power in redemption. In Luke 1:51, Mary's Magnificat celebrates: "He has performed mighty deeds with his arm." John 12:38 quotes Isaiah 53:1 — "To whom has the arm of the Lord been revealed?" — as the introduction to the Suffering Servant passage, indicating that Jesus is the ultimate revelation of God's saving arm. Acts 13:17 recalls the Exodus: "With mighty power he led them out." God's arm did not swing a sword but stretched out on a cross — the most paradoxical display of strength in history.