I don't recall ever using "pre-Haladin" but it is not an unreasonable expression.
"
Gwathuirim", in its
correct usage, should be applied only to the people of the
Second Age whom the
Numenoreans found living along the banks of the Gwathlo river. The name is used by
Tolkien in an essay published in
Unfinished Tales.
I, and perhaps others following my lead or duplicating my reasoning, have extended the name as a matter of convenience to refer to all the
peoples historically related to the Gwathuirim in Tolkien's writings: the Folk of Haleth (sometimes called
Haladin, but Tolkien eventually decided that name should only be applied to the family of the chieftains), the
Men of
Bree, the Men of Eryn Vorn, the
Dunlendings, the Men of the
White Mountains (including the
Dead Men of Dunharrow), and whomever their collective ancestors were.
Marachians is correctly applied only to those
Edain who followed Marach into
Beleriand, and their descendants (in Beleriand). I believe Tolkien used that name in one or two
places, but I cannot offer any citations. The Marachians had relatives in
Eriador and the lands beyond the
Misty Mountains (mostly in the lands beyond
Greenwood the Great), according to "
Dwarves and Men" in
The Peoples of Middle-earth. Some of the Marachians fled back to Eriador after the
Dagor Bragollach (those who survived at Estolad).
Beorians, like
Marachians, is properly only applied to those Edain who followed Balan (Beor) into Beleriand and their descendants. However, like the Marachians and the Folk of Haleth, the Beorians had relatives living in Eriador, and like the Marachians the Beorians also had relatives living in the lands beyond the Misty Mountains (mostly in the Vales of
Anduin and Greenwood the Great).
Tolkien wrote that each wave of migration established new homes, and successive generations produced migrations which left behind larger peoples than the groups going forward. So, the Edain who entered Beleriand (about 10,000 families in all) represented only a small fraction of their entire peoples.
Now, I have never come across the term "Borrim" before, but it is a suitable translation of "Folk of Bor" (I think -- I am really no linguist). The Folk of Bor, according to a footnote, had relatives in northern Eriador who became the oldest group of Men in northern Eriador
in the Second Age. They were not the oldest group of Men in Eriador by any means.
The
Rohirrim, the Men of
Dale, the Men of the Long Lake, and possibly other groups of
Northmen living along or near the Celduin, were descended from the Marachians' relatives who stayed in the lands east of Greenwood the Great. Before
The Peoples of Middle-earth was published, I used to speculate that the Edain who fled back to Eriador from Beleriand might have been the remote ancestors of the Northmen of
the Third Age, but there appears to be no support for that speculation in any of the Tolkien texts.
Nonetheless, the kinship between Marach's people and the ancestors of the Northmen is well attested in "Dwarves and Men".
The
Beornings and the Woodmen, and perhaps other groups of Northmen living in the Vales of Anduin and the Forest, were descended from those peoples who were akin to the Beorians who had remained in the Vales of Anduin and Greenwood the Great.
These peoples all intermingled a little bit, and the Northmen sent several waves of settlers to
Gondor during the Third Age. So, the Numenoreans and their Edainic cousins more than likely intermarried in both
Arnor and Gondor acorss the millennia.
