The words knaves, naves sound the same but have different meanings and spellings. Why do knaves, naves sound the same even though they are completely different words?
The answer is simple: knaves, naves are homophones of the English language.
Plural form of knave.
Plural form of nave.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.