The name was Latinized as Theodoricus or Theodericus, originally from a Common Germanic form *þeudo-rīks, which would have resulted in a Gothicþiuda-reiks. Anglicized spellings of the name during Late Antiquity and the Early Middle Ages include Theodoric, Theoderic, Theudoric, Theuderic. Gregory of Tours Latinized the name as Theodorus, in origin the unrelated Greek nameTheodore. As the name survived throughout the Middle Ages, it transformed into a multitude of forms in the languages of Western Europe. These include the High German form Dietrich, abbreviated Dieter, the Low German and Dutch form Diederik, or Dierik, abbreviated Dirck, Dirk, Dik or Diede, the NorwegianTjodrik, Diderik and Didrik. Of the Romance languages, French has Thierry and Italian, Portuguese and Spanish has Teodorico. The English forms Derek, Derrick and Terry have been re-introduced from the continent, from Low German, Dutch and French sources. The Welsh form Tudur is the origin of the name of the English Tudor dynasty.
Late Antiquity to Early Middle Ages
The earliest record of the name is in a Roman-era inscription, discovered in 1784 in Wiesbaden, edited in Codex inscriptionum romanarum Danubii et Rheni as no. 684: IN. H. D. D. APOLLINI. TOVTIORIGI, interpreted as In honorem domus divinae, Apolloni toutiorigi. This has given rise to a supposed "Apollo Teutorix" in 19th-century literature. Rhys opined that "the interest attached to the wordToutiorix is out of all proportion to its single occurrence". The existence of a genuinely Celtic nameTeutorix or Toutorix is uncertain, though Welsh Tudur, Old WelshTutir presupposes a precise cognate of Toutorix at least in ancient British Celtic. Rhys surmises that the "historical Teuton" bore a name of the Gaulish Apollo as adopted into early Germanic religion. The first known bearer of the name was Theodoric I, son of Alaric I, king of the Visigoths. The Gothic form of the name would have been Þiudareiks, which was Latinized as Theodericus. The notability of the name is due to Theoderic the Great, son of Theodemir, king of the Ostrogoths, who became a legendary figure of the Germanic Heroic Age as Dietrich von Bern. After the end of Late Antiquity, during the 6th to 8th century there were also several kings of the Franks called Theodoric. Finally, there was an early Anglo-Saxon king of Bernicia called Theodric.
Theodoric I, king of the Visigoths
Theodoric II, king of the Visigoths
Theoderic the Great, ruler of the Ostrogoths, Italy, and the Visigoths
Theodoric Strabo
Theuderic I, Frankish king
Theuderic II, Frankish king
Theuderic III, king of the Franks
Theuderic IV, king of the Franks
Theodric of Bernicia, 6th century Anglo-Saxon king
Saint Tewdrig , Welsh king of Gwent and Glywysing, who was martyred fighting the Saxons
While the Anglo-Saxon name Theodric became extinct in the Middle English period, it was adopted in Welsh as Tewdrig. The name remains popular in medieval German as Dietrich, and is adopted into French as Thierry. It is rendered in Medieval Latin as Theodoricus or as Theodericus. The Middle High German legend of Dietrich von Bern is based on the historical Theodoric, king of the Ostrogoths. The GermanDietrich von Bern is reflected as Þiðrekr af Bern in the Old Norse Thidrekssaga. The medieval German legend gives rise to the Dietrich of the Renaissance eraHeldenbücher. The Old Norse form of the name was Þjóðríkr. This became Tjodrik in Middle Norwegian. The Dutch form Derek was used in England from the 15th century. Similarly, the Scandinavian Tjodrik is attested for the 12th century, but it is replaced by the Low German forms Ditrik, Dirk in the late medieval period. The spread of the Dutch or Low German form to Middle Norwegian, Middle Danish and late Middle English or Early Modern English are part of a larger linguistic trend due to the influence of the Hanseatic League during this period.
Counts of Holland Dirk I, Dirk II, Dirk III, Dirk IV, Dirk V, Dirk VI, and Dirk VII
Modern era
The German form Dietrich was abbreviated to Dieter. The Low German and Dutch languages abbreviated Diederik as Dirk or Diede. French retains Thierry. The Scandinavian languages have borrowed Dirk and Diderik, replacing the native Tjodrik, while English borrowed Derek from Dutch and Terry from French.