Changing values of language.xml

Hello,

I'm trying to change some values of language output. Index for example
should still be index and not be changed to my local language.

I found out that in docbook the template gentext in common/l10n.xsl is
called which calls l10n.xml. In l10n.xml is a list of entities which
points to the xml language-file.
How can i override a special term like index in this language-file?

I tried to copy the template gentext in a xsl-file of my local directory
where all my stylesheets are lying which override the docbookstylesheets.
Then i did also copy l10n.xml and the language xml-file. I changed the
term of index to index and Index to Index but it didn't work. It's still
calling the xml-file from the docbook-directory.
Could somebody assist.

Kai