Surname Siwas (ศิวา 
, ศิวัสว์ , Siwas 
) , in all the world, is a rare cognomen. The cognomen Siwas is habitual in Indonesia, where it is a very rare surname, Malaysia, and Australia. Measured by absolute frequency, the name is most common in India, Indonesia, and Philippines. More frequently, Siwas is the forename as well as the last name.