Vasja

Vasja is a diminutive form of the name Vasily (Василий) in Slavic languages, particularly Russian, Slovenian, and Serbian. Vasily itself is derived from the Greek name Basileios (Βασίλειος), which means 'royal' or 'kingly'. The name gained popularity in the Orthodox Christian world due to several saints named Basil, most notably Basil the Great, one of the Cappadocian Fathers of the early Christian church.

Over centuries, as Christianity spread through Eastern Europe, the name Basileios was adopted and adapted into local languages, becoming Vasily in Russian, Vasil in Bulgarian and Macedonian, and Vasyl in Ukrainian. The diminutive forms like Vasja emerged as affectionate or informal ways to refer to someone named Vasily, much like 'Billy' for 'William' in English. While it started as a diminutive, Vasja is now often used as a standalone given name in some Slavic countries.