The Rohirrim

[Alchisiel]

I'm reading LOTR for the third time this year and I've come upon a passage that I never noticed before. It's Book 4 Chapter 5 The Window On The West Page 322. To be exact. Faramir is telling Frodo and Sam about the history of Gondor. This particular passage caught my attention:

But the stewards were wiser and more fortunate. Wiser, for they recruited the strength of our people from the sturdy folk of the sea-coast, and from the hardy mountaineers of Ered Nimrais. And they made a truce with the proud peoples of the North who often assailed us, men of fierce valour, but our kin from afar off, unlike the wild Easterlings or the cruel Haradrim

He later goes on to say that these people are the Rohirrim and also that they come from the Houses of Men specifically Hador. It's been a while since I've read the Silm but I don't remember reading that the House of Hador had assailed Gondor or any other house of Men. Does anyone have any information on this and is it in fact in the Silm if so where?