Garret
A garret is a finished, habitable attic. A gambrel roof or mansard roof is best suited to attic habitability. A garret can be an apartment, game room, etc and traditionally would have primarily held the domestic servants rooms.
Garret Media
The Garreteer's Petition by Turner, 1809
Carl Spitzweg, The Poor Poet (Der arme Poet), 1839, depicting a garret room