I'm not sure why this word got chosen. It just seemed right. I've never seen it used, but it isn't an obsolete or rare word, and the opportunities for use seem like they wouldn't be too rare; don't we all carry pennies from time to time?
Of the nature or colour of verdigris, or copper-rust.
Listening to: Musica Antiqua Köln - Reinhard Goebel - Musica Antiqua Köln - Reinhard Goebel - 02 - Concerto 5 2. Affettuoso