Cognomen Tsyku (Цику 
, Tsyku 
, Цыку 
) , all over the world, is a rare last name. The last name Tsyku is characteristic of Estonia, where it is a rare surname, Russia, and Ukraine. Measured by absolute frequency, it most frequently occurs in Russia, Ukraine, and Kazakhstan. Also, Tsyku is the forename as well as the last name.