From Icelandic or Norwegian foss, both from Old Norse fors (“waterfall”). Doublet of force (“waterfall”).
Meanings
(Northern-England) A waterfall.
Another of his flock was spotted garrotted, one found twisted and drowned at the bottom of a foss and a third split cleanly from scut to teeth. 2017, Benjamin Myers, The Gallows Pole, Bloomsbury, published 2019, page 101: