1590s, "pertaining to Attica," from Latin Atticus, from Greek Attikos "Athenian, of Attica," the region around Athens (see Attica). Attested from 1560s as an architectural term for a type of column base.
"top story under the roof of a house," 1855, shortened from attic storey (1724). The term Attic order in classical architecture meant a small, square decorative column of the type often used in a low story above a building's main facade, a feature associated with the region around Athens (see Attic). The word then was applied to "a low decorative facade above the main story of a building" (1690s in English), and it came to mean the space enclosed by such a structure. The modern use is via French. attique. "An attic is upright, a garret is in a sloping roof" [Weekley].