A gill or ghyll is a ravine or narrow valley in the North of England and parts of Scotland.
As a related usage, Gaping Gill is the name of a cave, not the associated stream, and Cowgill, Masongill and Halton Gill are derived names of villages.
These gills may be up to 200 feet (61 m) deep, which represents a significant physiographic feature in lowland England.
In the North Pennines, the word sike or syke[5] is found in similar circumstances.
This is particularly common in the Appleby Fells area where sikes significantly outnumber the becks and gills; it can also be seen in the name of Eden Sike Cave in Mallerstang.