Douglas Harper's Etymology Dictionary
foot-hills
also foothills; see foothill.
Usage examples of "foot-hills".
There was a beaten way, north-westward along the foot-hills of the White Mountains, and this they followed, up and down in a green country, crossing small swift streams by many fords.
To the South, far away, below the changing clouds, lay the broken, dark blue foot-hills of Kilimanjaro.