From Tolkien Gateway
Not to be confounded with: Sunlands, the name of Harad in the Common Speech

Sunlending was the name used by the Rohirrim of the land of Anórien, 'Sun-land'. It is mentioned in the song From dark Dunharrow in the dim morning, l. 15: "six thousand spears to Sunlending".[1]

The name Sunlending did not refer to the climate, but was rather 'heraldic', as Anórien was immediately attached to Minas Anor. Sunlending was thus connected to the name and the emblem of Anárion, brother of Isildur.[2]