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.
[dawr, dohr] 
