Our research began in 2009, in Workington Public Library.
We found the following sources very useful:
1. The Historical Gazetter of England's place-names (19 different spellings)
2. The Place-Names of Cumberland, A. M. Armstrong, A. Mawer, F. M. Stenton, and Bruce Dickins, Cambridge 1950.
3. The Place-Names of Cumberland and Westmorland , by Prof. WJ Sedgefield, Manchester University Press, 1915. (8 different spellings)