Kassian is a German and Polish spelling of Cassian, from the Roman family name Cassianus, which derives from Cassius and is usually explained as "hollow" or "empty". Saint John Cassian, a 5th-century monk, brought Eastern monastic practice to the West. In the United States Kassian first registered in 2017 at number 4397, peaked at number 2676 in 2023 and sits at number 2959 in 2025.