Door
Old English duru, dor, of Germanic origin; related to Dutch deur ‘door’ and German Tür ‘door’, Tor ‘gate’; from an Indo-European root shared by Latin foris ‘gate’ and Greek thura ‘door’.
wiktionary
From Middle English dore, dor, from Old English duru(“door”), dor(“gate”), from Proto-Germanic *durz, from Proto-Indo-European *dʰwṓr, from *dʰwer-(“doorway, door, gate”). Cognate with Scots door(“door”), Saterland Frisian Doore(“door”), West Frisian doar(“door”), Dutch deur(“door”), German Low German Door, Döör(“door”), German Tür(“door”), Tor(“gate”), Danish and Norwegian dør(“door”), Icelandic dyr(“door”), Latin foris and foras, Ancient Greek θύρα(thúra), Albanian derë pl. dyer, Central Kurdish دەرگە (derge), derî, Persian در (dar), Russian дверь(dverʹ), Hindi द्वार(dvār) / دوار (dvār), Armenian դուռ(duṙ), Irish doras, Lithuanian durys.
etymonline
door (n.)
"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." The difference (no longer felt in Old English) was that the former came from a singular form, the latter from a plural.
Both are from Proto-Germanic *dur-, plural *dures (source also of Old Saxon duru, Old Norse dyrr, Danish dr, Old Frisian dure, dore, dure, Old High German turi, German Tr). This is from PIE root *dhwer- "door, doorway."
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.
Figurative sense of "means of opportunity or facility for" was in Old English. Phrase door to door "house to house" is from c. 1300; as an adjective, in reference to sales, by 1902.
A door is what a dog is perpetually on the wrong side of. [Ogden Nash]
