I don't know of a dictionary as such, but I have seen reference to at least one book on this subject. The name escapes me, of course, sorry about that, but someone here is sure to know. Your idea of a separate forum on differing usages seems good to me. I too am fascinated by this subject. Some years ago a colleague of mine (ex-Yorkshire, now Oz) who was visiting the US on business was invited to the home of one of his contacts for dinner. The time came when the hostess suggested that perhaps people would like to eat, whereupon my friend announced: "Yes, I am feeling rather peckish", and wondered why everyone fell about laughing.