Extending this idea a tad. You could use it to encode messages.

Pass message through textonym encoder, generating "new" words and a key to indicate which option the original is within each set of textonymns.

Send message and key separately.

To decode get textonyms for each coded word, use key to select which of these is original.

Advantages include message doesn't look encrypted so if mail system blocks other forms of encryption this may still work.

Limitations include both parties need same word list to ensure correct decoding/encoding. Possible that there may be no textonyms for enough words to make encoded message readable.

Enhancements would be to have unique exchange coding between letter and phone digit. Interceptor would then need 3 parts to get message. The encoded message, encoding key and exchange key.

OK so it's not very secure but it sounds fun. With some clever coding one may end up with an encoded message that's actually readable too.