Cognomen Cassianus (Cassian 
, Cassano 
, Cassianus 
) , all over the world, is a common last name. The family name Cassianus is habitual in Italy, where it is quite a common surname, Malta, and Tanzania, where it is quite a rare surname. Measured by absolute frequency, this name is the most popular in Italy, the United States, and Tanzania. Much less frequently, Cassianus is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Cassian | Tanzania, Argentina, Italy, Brazil, United States |
| Cassano | France, Argentina, Italy, Brazil, United States |
| Cassianus | Indonesia, India, Malaysia, Tanzania |
| publius nonius asprenas caesius cassianus first century AD Roman senator and consul (b. 50) |
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| tiberius licinius cassius cassianus suffect consul 147 AD (b. 150) |
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