What's the difference between i.e. and e.g.?
Middle English merger of Old English dor (neuter; plural doru) "large door, gate," and Old English duru (fem., plural dura) "door, gate, wicket;" both from Proto-Germanic *dur- (cf. Old Saxon duru, Old Norse dyrr, Danish dør, Old Frisian dure, Old High German turi, German Tür).
The Germanic words are from PIE *dhwer- "a doorway, a door, a gate" (cf. Greek thura, Latin foris, Gaulish doro "mouth," Gothic dauro "gate," Sanskrit dvárah "door, gate," Old Persian duvara- "door," Old Prussian dwaris "gate," Russian dver' "a door").
The base form is frequently in dual or plural, leading to speculation that houses of the original Indo-Europeans had doors with two swinging halves. Middle English had both dure and dor; form dore predominated by 16c., but was supplanted by door.
A door is what a dog is perpetually on the wrong side of. [Ogden Nash]
moved on pivots of wood fastened in sockets above and below (Prov. 26:14). They were fastened by a lock (Judg. 3:23, 25; Cant. 5:5) or by a bar (Judg. 16:3; Job 38:10). In the interior of Oriental houses, curtains were frequently used instead of doors. The entrances of the tabernacle had curtains (Ex. 26:31-33, 36). The "valley of Achor" is called a "door of hope," because immediately after the execution of Achan the Lord said to Joshua, "Fear not," and from that time Joshua went forward in a career of uninterrupted conquest. Paul speaks of a "door opened" for the spread of the gospel (1 Cor. 16:9; 2 Cor. 2:12; Col. 4:3). Our Lord says of himself, "I am the door" (John 10:9). John (Rev. 4:1) speaks of a "door opened in heaven."