Many places in Lancashire were mentioned in medieval documents and there are many books and articles about their origins. Ekwall’s 1922 Place-names of Lancashire is a classic and is available copyright free.
Here is the contents page of this important 1922 study of the origin of Lancashire place-names.
Note This is a large file of 45 megabytes!
You will need the free Adobe Reader program to view the book, if it is not installed you can download it here.