(n-)dôr (“land, dwelling place”) + cant (“shape”) + as (#abstract collective suffix) + iaur (“old”) #The suffix -as probably denotes “a complete set of different things of one kind”.
Dorgannas Iaurnoun. account of the shapes of the lands of old
dorgannas iaurproper name. [Account of the] Shapes of the Lands of Old
A treatise on the geography of Beleriand, translated “account of the shapes of the lands of old” (WJ/192), a combination dôr “land”, the lenited form gannas of (otherwise unattested) cannas “shape” and iaur “old”. Despite the pluralities in the translation, the Sindarin forms are singular, so a more literal translation would be “Shape of the Land of Old”.