have you searched through all of the files in the minecraft.jar? if not, thats where i would start
nvm i found it: go into your minecraft.jar and find the folder called "lang" in there is a language.txt and a bunch of files. Then open the file en_US.lang as a reference (with a text editor) and create a new file with any name you want. copy/paste the en_US and change the words...
when your done with that, go into the languages.txt and add in your file the same way its written there
