NOTES ON SURNAMES (HULL) 6
CAYGILL Fred Caygill was born Sculcoates 1855 (Yorks. DMB). A surname well represented in Yorkshire and Durham, but of unknown origin. It looks like a place name, but I have not found any such. If it is, the -gill component probably means “ravine”, with the Cay possibly meaning “crow”.
The above is all that I have on this name. There is more here –
which looks reliable.