Typically, the "baby name" websites say that Devlin means brave or fierce. According to Wikipedia: The O'Develins name in Irish is Dobhuilen which means "Raging Valour."The book "The Story of an Irish Sept, the O'Develins of Tyrone, Now Represented by the Families of Devlin, Develin, Develyn, D'Evelyn, Develen, Develan, Develon, Devellen, Devellin, Etc" by Joseph Chubb Develin also mentions the meaning of the name being "Raging Valour."Do means something like burn or burning. Buile means something like frenzy, madness, or mania.