The adjective Derbaios designates someone from Derbe, a city in Lycaonia (modern south-central Turkey) that Paul visited on his first and second missionary journeys. It appears describing Gaius of Derbe, one of Paul's travel companions.
Derbe was a strategic city on Paul's first missionary journey — the turning point where, after being stoned and left for dead in Lystra, Paul pressed on to Derbe and made many disciples (Acts 14:21). The fact that a Derbean, Gaius, later traveled with Paul as a trusted companion shows how missionary work creates lasting bonds across cultural lines. Derbe represents the fruit of suffering: Paul nearly died near there, yet God used that city to produce lasting disciples.