A vocabulary of landscape — a landscape of words 1367 entries

force

FORS
A force is a waterfall, in the northern English uplands. High Force and Low Force on the Tees, Aira Force above Ullswater, Scale Force in Buttermere, and Hardraw Force in Wensleydale all carry it. The word is not a general English term and does not appear south of the old Norse settlement, so a waterfall in Yorkshire is a force and one in Devon is not.
Etymology
The word is Old Norse for a waterfall and arrived with Danish and Norwegian settlement in the north and east of England, where it stayed. It has nothing to do with the ordinary English force meaning strength, which came from Latin by way of French, and the two words simply collided on the same spelling. Icelandic and Norwegian still use the Norse word, which is why waterfalls in Iceland end in foss.
Notes
A walk in the Lake District or the Dales can be conducted almost entirely in Norse. The stream is a beck, the ravine it runs in is a gill, the waterfall is a force, the lake is a tarn, the hill is a fell, and the valley is a dale.