Derek is a masculine given name. It is the English language short form of Diederik, the Low Franconian form of the name Theodoric. Theodoric is an old Germanic name with an original meaning of "people-ruler" or "lead the people". Common variants of the name are Derrek, Derik, Deryck (included here), as well as Derrick and Derick. History. . The English form of the name arises in the 15th century, via import from the Low Countries. The native English (Anglo-Saxon) form of the name was Deoric or Deodric, from Old English Þēodrīc, but this name had fallen out of use in the medieval period.
https://en.wikipedia.org/wiki/Derek