An elevated, uncultivated stretch of land in northern England or Scotland, a fell gains height and becomes a hill or even mountain in the northwest of England. It can be in some cases a pasture land on the top or side of a hill, but the fell is definitely treeless, because it is used in conjunction with “Frith” – a woods:

Wheresoeuer ye fare by fryth or by fell.

1486   Bk. St. Albans sig. ej  

And now I am head-over-heels in love with that phrase, please be on the watch for it anywhere that I’ve got access to a keyboard…

But why did this word “Fells” as it is used in the dwarves’ song not make it into the first pass on uncommon words back in ’15? It’s not a form of “Fall”. It’s not in my list of the ten thousand most common words. It’s not on the Great Spreadsheet as a word that would have been passed through as “uncommon”. I’m afraid, Word Fans, that I may have made a human error and whooshed it out of a list somewhere. Good thing this project is ongoing!!

• 01.074 In hollow halls beneath the fells.
• 15.038 In hollow halls beneath the fells.

“fell, n.3.” OED Online, Oxford University Press, September 2019, http://www.oed.com/view/Entry/69064. Accessed 27 October 2019.