Upbourn is a hamlet located in Rohan, south of Edoras on the banks of the Snowbourn in the valley of Harrowdale.
The name is a modernisation of the Old English Upburnan as would represent Rohirric. 
It derives from the fact that the hamlet was some way "up" the river Snowbourn.
As Tolkien noted, up- is used in English place-names for river-side villages (as Upavon in Wiltshire), especially in contrast to larger places near its mouth (as Upwey above Weymouth).
- ↑ 1.0 1.1 1.2 J.R.R. Tolkien, "Nomenclature of The Lord of the Rings" in Wayne G. Hammond and Christina Scull (eds), The Lord of the Rings: A Reader's Companion, p. 778