The name Theodrichos (pronounced theoDORichos) is cited in *Lexicon of Greek Personal Names* (an Oxford University project,
http://www.lgpn.ox.ac.uk/names2.html) as a bona fide central Greek name.
The above compilation excludes Byzantine-era names, so it appears that the Theodoric/Theodorichos was in fact not a name coined by our Gothic friend.