The Serdi were a Celtic tribeThe Cambridge Ancient History, Volume 3, Part 2: The Assyrian and Babylonian Empires and Other States of the Near East, from the Eighth to the Sixth Centuries BC by John Boardman, I. E. S. Edwards, E. Sollberger, and N. G. L. Hammond, , 1992, page 600: "In the place of the vanished Treres and Tilataei we find the Serdi for whom there is no evidence before the first century BC. It has for long being supposed on convincing linguistic and archeological grounds that this tribe was of Celtic origin" inhabiting Thrace. They settled around Serdica (modern-day Sofia, Bulgaria), in the place of the vanished Thracian tribes of the Treres and Tilataei.SE´RDICA which reflects their ethnonym. They would have established themselves in this area during the Celtic migrations at the end of the 4th century BC, though there is no evidence of their existence before the 1st century BC. Serdi are among traditional tribal names reported into the Roman era.M. B. Shchukin, Rome and the Barbarians in Central and Eastern Europe: 1st Century B.C.-1st Century A.D. They were gradually Thracianized over the centuries but retained their Celtic character in material culture up to a late date,The Cambridge Ancient History: pt. 1. The prehistory of the Balkans. The Middle East and the Aegean world, tenth to eighth centuries, B.C. 1991, p. 600. emerging as a mixed Thraco-Celtic tribe.John Moss (2025) The Celtic Tribes. Origins, Ancestry & The Warrior Class. Pen & Sword Books. According to other sources they may have been of Thracian origin.Britannica
See also History of Sofia List of ancient tribes in Thrace and Dacia
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