Word Origin & History
M.E. merger of O.E. dor (neut.; pl. doru) "large door, gate," and O.E. duru (fem., pl. dura "door, gate, wicket"), both from P.Gmc. *dur-, from PIE *dhwer-/*dhwor- "a doorway, a door, a gate" (cf. Gk. thura, L. foris, Gaul. doro "mouth," Goth. dauro "gate," Skt. dvárah "door, gate," O.Pers. duvara-
"door," O.Prus. dwaris "gate," Rus. 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. M.E. 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]
First record of dooryard is c.1764, Amer.Eng.; doorstep is from 1810.