Cassius is an old Roman family name, usually traced to the Latin cassus and explained as "hollow" or "empty", though the connection is not certain. Gaius Cassius Longinus led the plot against Julius Caesar, and the boxer Muhammad Ali was born Cassius Clay. The name was rare in the United States at the turn of the century, entered the top 1000 in 2011, peaked at number 487 in 2021 and ranks number 583 in 2025.