Keegan is an Irish surname, from Mac Aodhagáin, that means "son of Aodhagán", a pet form of Aodh, the old Irish word for fire, so it is usually read as "little fiery one". In America it joined the wave of Irish surnames used as first names, alongside Brennan and Keenan. Keegan ranked number 285 in 2000, peaked at number 222 in 2007 and has drifted to number 621 in 2025.