In autumn 1710, as a young prison guard in Bytca (Nagybiccse), he helped the imprisoned Tomas Uhorcik escape. After the lost Battle of Trencin, Janosik was recruited by the Habsburg army. He fought with the Kuruc insurgents when he was fifteen. He grew up in the village of Terchova (Tyerhova) in the Habsburg monarchy's Kingdom of Hungary area (present-day Zilina District in northwestern Slovakia). His first name, ("George" in English) has been a very common name all over Europe and his last name is still common around his birthplace. His godparents were Jakub Merjad and Barbara Kristofikova. His parents were Martin Janosik and Anna Cisnikova from Terchova. Janosik was born shortly before his baptism on January 25, 1688. During the anti-Nazi Slovak National Uprising, one of the partisan groups bore his name. The image of Janosik as a symbol of resistance to oppression was reinforced when poems about him became part of the Slovak and Czech middle and high school literature curriculum, and then again with the numerous films that propagated his modern legend in the 20th century. However, the legend was also shaped in important ways by the activists and writers in the 19th century when Janosik became the key highwayman character in stories that spread in the north counties of the Kingdom of Hungary (much in present Slovakia) and among the local Gorals and Polish tourists in the Podhale region north of the Tatras (Tatra). The actual robber had little to do with the modern legend, whose content partly reflects the ubiquitous folk myths of a hero taking from the rich and giving to the poor. The legend was also known in neighbouring Silesia, the Margraviate of Moravia and later spread to the Kingdom of Bohemia.
According to the legend, he robbed nobles and gave the loot to the poor, a deed often attributed to the famous Robin Hood.