Etymology. “movable barrier, commonly on hinges, for closing a passage into a building, room, or other enclosure,” c. 1200, a Middle English merger of two Old English words, both with the general sense of “door, gate”: dor (neuter; plural doru) “large door, gate,” and duru (fem., plural dura) “door, gate, wicket.” Middle English had both dure and dor; the form dore predominated by 16c. but was supplanted later by door. The oldest forms of the word in IE languages frequently are dual or plural, leading to speculation that houses of the original Indo-Europeans had doors with two swinging halves.