Abbott-Smith Manual Greek Lexicon
σύν-τροφος (G4939)
1 σύν-τροφος , -ου, ὁ ( συντρέφομαι , to be brought up together ) [in LXX: III Ki 12:24 , I Mac 1:6 R, II Mac 9:29 * ;] prop., one nourished or brought up with, a foster-brother : Ac 13:1 EV. In Hellenistic usage, as a court term, an intimate friend of a king (v. Deiss., BS , 305, 310 f.): Ac 13:1 (cf. also MM, xxiv).†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain