Predefine categories for your theme

Hi

I am building a theme and the frontend for it will heavily depend on the use of 4 different categories. I really would like to predefine those 4 categories in my code, instead of adding them in the WP Backend UI.
Is there a way to achieve this?

I know I can program taxonomies, but I need categories.
Or predefined terms for a custom taxonomy.

Thanks for any help here.
I searched the web, but I would only find tutorials how to add categories :S.

Cheers