According to some sources,the men of Numenor discovered a continent called Morinore (although it is a Quenya calque for Mordor it is not Mordor, it should be a place in the region of Australia/ New Zealnd/Papua).
What is known about the place? In MERP wikia it is called Southernesse but did not find anything relevant about it...
I'm pretty sure that "Morinore" is actually the Dark Lands. This would make sense, because the Numenoreans went there several times on their traveles. Also, according to several sources, Earendil (pretty much the first Numenorean) went there on his travels, and may have even stayed Ungoliant there.
I could not find the name Morinore in the History of Middle-earth (HoMe) Index, but since the stem 'mor-' means 'dark', and you talk about a continent discovered by the Numenoreans, I concur with Turinguy that the reference is indeed to the Dark Lands that lie to the south-east of Harad (the first map on this page lists it as Hyarmenor - www.tolkienforums.com/secondagemaps.htm).
Indeed in the Silmarillion (the Akkalabeth) it is implied that the Numenorean mariners sailed there during the Second Age, and some tales of Earendil the Mariner mention him as going to the South and there slaying Ungoliant, but these should not be considered canon, if I remember the texts correctly (because they appear in HoMe and have likely been changed or abandoned by the author).
Later edit: I just stumbled across a website with maps (they are not canon, most of them pertain to RPG games, but their quality is often remarkable - http://lindefirion.net/maps/). On this page you can find two maps of the world during the Second and Third Ages that label the Dark Lands as 'Morenor'. Here they are (just take into consideration that they introduce elements not found in Tolkien's original maps or ideas):
http://lindefirion.net/maps/secondagearda.jpg
http://lindefirion.net/maps/Ambarkanta2.jpg
-- Edited by John Wain on Friday 26th of May 2017 09:16:40 AM