The name Teikō is taken from the kanji:
"TEI" which means sovereign
“KŌ” which means light.
Although many folklores has tried to explain the origin of the name Teikō, historical records shows that the most factual is the visitation of the Britannian explorer and missionary Renfred Destain during his expedition of the western coast in 1798. It was Renfred who first coined the place as Teikō which is Kaijo in the modern day period as referred to his journals in which he explained his exciting encounters with the gods during his spiritual exercises. Eventually, upon his return to Britannia, the whole surroundings lands of the present day Kaijo has been collectively termed as Teikō.
The official name of the Commonwealth of Teikō has changed several times in the course of the country’s history. During the colonization of the Holy Britannian Empire, the entire country was named Districto Eleven (District 11) as referred to as being the 11th district to be colonized by the Britannians. From the period of the commonwealth years until the proclamation of independence the country is called Commonwealth of Teikō. From the reunification in 1986 after the civil war, the name Teikō began to appear and it has since been the country’s common name. As of today, the name Commonwealth of Teikō is being used again to distinguish it from the Teikō prefecture with the full official name of Independent Principality of the Commonwealth of Teikō recognized internationally.
As for romanization, the Commonwealth of Teikō recognizes the word "Teiko" rather than "Teikou" when written in English for this has been the culture for many decades.
Source: National Archives
