You may want to look into a Kindle feature called X-ray that allows extra information to be added outside of the regular content of a book. Amazon describes it this way: X-Ray is a unique Kindle eBook feature that allows readers to learn more about a character, topic, event, place, or any other term, simply by pressing and holding on the word or phrase that interests them.
See the KDP help topic
X-Ray for Authors for details on how to generate it.