1590s, "pertaining to Attica" (q.v.), the region around Athens, from Latin Atticus "Athenian," from Greek Attikos "Athenian, of Attica." The Attic dialect came to be regarded as the literary standard of ancient Greece, and it passed into the koine of the Alexandrine and Roman periods. Attested from 1560s as an architectural term for a type of column base.
"top story under the roof of a house," by 1807, shortened from attic story (1724). Attic 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 by architects to "a low decorative facade above the main story of a building" (1690s in English), and it then 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].