Of all the words and phrases that are common in or unique to Mormonism, added upon is perhaps the most connected with a work of literature. Though perhaps infrequently used today in Mormon vernacular (except to refer to the book Added Upon), in the past it was frequently used in discussing Mormon doctrine, and it is still used today because it appears in scripture and refers to a key concept of that doctrine, one touched on in my recent definition of the Mormon use of the word exaltation.
Unlike exaltation, however, added upon is today almost exclusively Mormon.