Mixing l18n string from my plugin with WordPress’ translations

Only use the internal translations if you use the complete string without any addition. Grammar rules, writing directions etc may be different in your user’s language and your order may not match their needs.

You example would be Taxonomiename or Name der Taxonomie in German. How should a translator handle this?

So, use:

<?php echo _x('Taxonomy Name', 'text input label', 'my_plugin_domain'); ?>