1580s, "foreign, from beyond the sea," from earlier oversea "transmarine, of or pertaining to movement over the sea," 1550, from over- + sea. The adverb, "across or beyond the sea," is attested from 1580s, from earlier adverb oversea (late Old English). As an adjective, 1892 in English; earlier oversea, "of or pertaining to movement over the sea"(1749). Popularized during World War I as a British euphemism for "colonial." As a noun, "foreign parts," by 1919.