1911 Encyclopædia Britannica/Solar
SOLAR, SOLLER (Lat. solarium, Fr. galetas, Ital. solaio), in architecture, a room in some high situation, a loft or garret, also an elevated chamber in a church from which to watch the lamps burning before the altars. The Latin solarium was used principally of a sundial, but also of a sunny part of a house.