"round, vaulted roof," 1650s, from French dome (16c.), from Provençal doma, from Greek doma "house, housetop" (especially a style of roof from the east), related to domos "house" (see domestic).In the Middle Ages, German dom and Italian duomo were used for "cathedral" (on the notion of "God's house"), so English began to use this word in the sense "cupola," an architectural feature characteristic of Italian cathedrals. Used in U.S. also with reference to round summits of mountains.