CHDK Wikia: Languages The link to that page is on the homepage for CHDK in the "Basic Articles" section. (RTFM!)
Always try to use the language file the author provides for his particular build, rather than one of the generic ones from tha Languages page, as those aren't updated to reflect the myriad builds of CHDK. While they will still work for most of the menus and features, many of the builds have features (menu options) that aren't covered by the generic language files posted there.
I tried to read the manual, but the wiki is rather rambling and sprawling; I used google to search the wiki for "Language file" and did not find the page you refer to.
Thanks for your help though - that IS is the information I need.
BugBear