Casimir is the English and French form of the Polish Kazimierz, from the Slavic kazati, to proclaim or destroy, and mir, peace, usually read as "proclaimer of peace" or "destroyer of peace". Saint Casimir, a 15th-century prince, is the patron saint of Poland and Lithuania, and Casimir Pulaski, the Polish cavalry officer, is a hero of the American Revolution. The name has gained ground among parents who like old European names: from about number 3300 in 2015 to number 2039 in 2025, its best rank so far.