Source : Webster's Revised Unabridged Dictionary (1913)

Czechs \Czechs\ (ch?ks), n. pl.; sing. {Czech}. [Named after
   their chieftain, Czech.] (Ethnol.)
   The most westerly branch of the great Slavic family of
   nations, numbering now more than 6,000,000, and found
   principally in Bohemia and Moravia.