The Northerland, the Norland, the Northern Lands, the Northlands, the Northern world, and the North, were vague terms for various lands of Middle-earth.
The regions of Anfauglith, the Ered Engrin, and Hithlum (Dor-lómin and Mithrim) were all described as belonging to the Northlands. During the late Third Age, Boromir referred to the regions north of the Tharbad as Northerland. The term was also used to refer to the Forodwaith. The Bree-land in Eriador were considered to be Northern Lands. While at Rivendell, Bilbo Baggins poetically described the sunken Beleriand as Norland, a shortened form of Northerland, in The Short Lay of Eärendel: Eärendillinwë. During the Council of Elrond, Gimli described Khazad-dûm as being the greatest realm of the Northern world.
Trivia
Strangely, although "north" and "land" were used frequently in various combinations, "Southland" or "South land" was only used to refer to the Dark Land and not Harad which was a known region south of where most of the legendarium was set, but called alternate names such as Sunlands or Sutherland. The TV series The Lord of the Rings: The Rings of Power created the term "Southlands" for Mordor before it was known by that name in the show's timeline.