Customization of the text output of <keycap function="..."/>

[Phillip Kent <phillip.kent@gmail.com>]

I want to customize the text output of <keycap function="backspace"/>
and <keycap function="delete">
[the first I think is ugly and the second doesn't correspond to all of
the keyboards I have looked at which have a primary 'Delete' key not
'Del']

I can see this is a language/localization issue. Is there a simple(r)
way of customizing without have to customize a language setting?

Thanks Phillip