https://en.wikipedia.org/wiki/Czech_lands
The term Czech lands has been used to describe different things by different people. While the Czech name of Bohemia proper is Čechy, the adjective český refers to both "Bohemian" and "Czech". The non-auxiliary term (i.e. the term used in official Czech geographical terminology lists) for the present-day Czech lands (i.e. Bohemia, Moravia, Czech Silesia) is Česko, documented …