Custom taxonomy names (and custom post type names) need to comply to a very specific set of rules, otherwise you will encounter pitfalls that there are no work around for.
Here is a guide line when choosing names for custom taxonomies (and custom post types)
- The following are not allowed in custom taxonomy names and custom post type names
- Capital letters or camelcase
- Any type of special character, except underscores (
_) - Spaces
- More than 32 characters for taxonomies and 20 for post types
- Any reserved names, and please note, this goes for any custom naming convention, not just taxonomy names.
- If there are more than one word in a taxonomy name, they have to be separated by underscores, not hyphens (
-). I have been challenged that hyphens are the way to go for SEO in URL’s for taxonomy names. It is true, that is why there are rewrite rules to adjust your URL accordingly. Never change taxonomy names or post type names for URL SEO purposes