Billie the Kid vs Bonney

Billie the Kid and Bonney both are nouns.

Word	Noun	Adjective	Verb	Adverb
Billie the Kid	Yes	No	No	No
Bonney	Yes	No	No	No

As nouns, Billie the Kid and Bonney are synonyms defined as:

Billie the Kid and Bonney: United States outlaw who was said to have killed 21 men (1859-1881)

Other synonyms of Billie the Kid include Billy the Kid, William H. Bonney.

Billie the Kid (noun)	Bonney (noun)
United States outlaw who was said to have killed 21 men (1859-1881)	United States outlaw who was said to have killed 21 men (1859-1881)