Cognomen Яну (Janu 
, Yanu 
, Ianu 
) , in all the world, is a common family name. The cognomen Яну is characteristic of Estonia, where it is quite a common surname, Qatar, and Czechia. Measured by absolute frequency, it is the most numerous in India, Indonesia, and Bangladesh. More prevalently, Яну is the forename as well as the last name.