encoding vs secret writing

encoding and secret writing both are nouns.

Word	Noun	Adjective	Verb	Adverb
encoding	Yes	No	No	No
secret writing	Yes	No	No	No

As nouns, secret writing is a hypernym of encoding; that is, secret writing is a word with a broader meaning than encoding:

Other hypernyms of encoding include coding, cryptography, steganography.

encoding (noun)	secret writing (noun)
the activity of converting data or information into code	act of writing in code or cipher
	a piece of writing in code or cipher