John Casey

(male) English form of Latin Io(h)annes, New Testament Greek Iōannēs, a contracted form of the Hebrew name Johanan ‘God is gracious’ (the name of several different characters in the Old Testament, including one of King David's ‘mighty men’). John is the spelling used in the Authorized Version of the New Testament. The name is of great importance in early Christianity: it was borne by John the Baptist (the precursor of Christ himself, who baptized sinners in the River Jordan), by one of Christ's disciples (John the Apostle, a fisherman, brother of James), and by the author of the fourth gospel (John the Evangelist, identified in Christian tradition with the apostle, but more probably a Greek-speaking Jewish Christian living over half a century later). The name was also borne by many saints and by twenty-three popes, including John XXIII (Giuseppe Roncalli, 1881–1963), whose popularity was yet another factor influencing people to choose this given name. It was also a royal name, being borne by eight Byzantine emperors and by kings of Hungary, Poland, Portugal, France, and elsewhere. Among numerous bearers of note in recent times have been American president John F. Kennedy (1917–63) and British pop singer John Lennon (1940–80). In its various forms in different languages, it has been the most perennially popular of all Christian names.

Irish: reduced Anglicized form of Gaelic Ó Cathasaigh ‘descendant of Cathasach’, a byname meaning ‘vigilant’ or ‘noisy’.