Last name Sydir (Сидор 
, Сидір , Sydir 
) , in all the world, is quite a common cognomen. The cognomen Sydir is habitual in Ukraine, where it is quite a common surname, Belarus, where it is quite a rare surname, and Kazakhstan, where it is a rare surname. In absolute terms, it is the most numerous in Eastern Europe, particularly Ukraine, Belarus, and Russia. Very seldom, Sydir is the forename as well as the last name.