Doohan is an ancient Irish surname, its oldest origins are found on Tory Island, County Donegal, Ireland. Doohan is the English translation of Dhubghain (dubh=black). The name is derived from Dubhgain (Duggan), where the 'g' is softened by a 'gh'. Notable people with the name include:
References
Doohan Wikipedia(Text) CC BY-SA