Where does “ján” come from?

ján (Slovak) comes from Latin Iōannēs, from Ancient Greek Ἰωάννης, from Hebrew יוחנן, from Hebrew חנון, from Moroccan Arabic خنونة, from Arabic خُنَّة.

ján (Slovak): Persons of the Christian Bible: John the Baptist; and names possibly referring to one, two or three persons, frequently called "Saint": John the Apostle, John the Evangelist and John of Patmos (also called John the Divine or John the Theologian)