The Hebrew word arba means 'four,' the cardinal number. It is also the name of a legendary Anakim giant — the 'greatest man among the Anakim' (Joshua 14:15) — after whom Hebron was formerly called Kiriath-arba, 'City of Four' or 'City of Arba.'
The number four carries rich symbolic weight in Scripture: four corners of the earth, four winds, four living creatures before the throne. But Arba the giant represents human power and pride in opposition to God's people. Yet God gave Israel victory over the sons of Arba (the Anakim), demonstrating that no spiritual giant — however fearsome — can withstand the LORD's appointed leader. Caleb, at 85 years old, drove out the sons of Anak from Hebron, turning the City of Arba into a testimony of God's faithfulness.