Jack

Jack began in the Middle Ages as a pet form of John. People made nicknames like Jankin by adding a small ending to John, and over time these were worn down to Jack. John itself goes back to a Hebrew name meaning “God is gracious”, and its Irish form is Seán. Jack has long since become a name in its own right rather than a nickname.

Jack first appears in the CSO records in 1970, and it stayed rare until the late 1980s. Then it rose very quickly, reaching number 1 in 2000. It was the top boys’ name in most years after that, and 1,151 boys were named Jack in 2008, its biggest year. In 2025 it slipped to second place. It is just as familiar in Northern Ireland, where it was also second in 2025.