wordbook vs onomasticon

wordbook and onomasticon both are nouns.

Word	Noun	Adjective	Verb	Adverb
wordbook	Yes	No	No	No
onomasticon	Yes	No	No	No

As nouns, onomasticon is a hyponym of wordbook; that is, onomasticon is a word with a more specific, narrower meaning than wordbook:

Other hyponyms of wordbook include dictionary, lexicon, vocabulary, gloss, glossary, synonym finder, thesaurus.

wordbook (noun)	onomasticon (noun)
a reference book containing words (usually with their meanings)	a list of proper nouns naming persons or places