Where does “プロシア” come from?

プロシア (Japanese) comes from English Prussia, from New Latin Prussia.

Ancestry of “プロシア”, step by step

StepLanguageWordMeaning
1EnglishPrussiaA country known for exceptional military professionalism in her region. Historically used for Bulgaria as the "Prussia of the Balkans"
2New LatinPrussia
Every word from New Latin PrussiaEvery word from English Prussia