Epithet and Key word

Epithet noun - A descriptive or familiar name given instead of or in addition to the one belonging to an individual.

Key word and epithet are semantically related In some cases you can use "Key word" instead a noun "Epithet".

Key word noun - A significant word used in indexing or cataloging.

Epithet and key word are semantically related in name topic. You can use "Epithet" instead a noun phrase "Key word".