English
mailpiece
From mail + piece; part of the business jargon of postal services and mail marketers for more than a century, but not common among the general public until the 21st century.
Today it means
noun (countable) A piece of mail, that is, an item of (physical) mail; especially, an item of flat envelope form factor as contrasted with an item of package form factor.
Language periods are conventional ranges, not dates for this word.
Etymograph / mailpiece