The surname Rusnok is found throughout areas of the Carpathian Mountains from contemporary Ukraine to Moravia in Czech Republic. The surname comes from the ethnonym RUSNAK, which designated a (male) person of Greek Catholic or Orthodox faith or of East Slavic language. RUSNAK is in some places a synonym for the ethnonyms Lemko, Rusyn, etc. Today many people in eastern Slovakia who claim Slovak nationality also use Rusnak to designate a regional or ethnographic identity. The form RUSNOK exhibits the phonological change of long a > o, which took place in various Polish dialects. Thus, it is likely that the particular form RUSNOK arose on territory that was linguistically Polish. J. Piszczor