Early 17th century; earliest use found in Arthur Gorges (d. 1625), poet and translator. From the name of the Capitol + -ian, after classical Latin Capitōlius, adjective.
Definition of Capitolian in US English:
Capitolian
adjectiveˌkapɪˈtəʊlɪən
poetic
= Capitoline.
Origin
Early 17th century; earliest use found in Arthur Gorges (d. 1625), poet and translator. From the name of the Capitol + -ian, after classical Latin Capitōlius, adjective.