The botanical metaphor “evergreen” is now used for whatever exhibits an enduring freshness, success, or popularity. The term originally appeared in the 17th century:
1640s in reference to trees and shrubs, from ever + green (adj.). From 1660s as an adjective;
but only more than two centuries later it started to be used metaphorically
figurative sense from 1871. (Etymonline)
Checking the usage of evergreen with Ngram for the second half of the 19th century, it appears there are no usage instances in the figurative sense.
So, what are the earliest usage of evergreen used figuratively? What was the metaphor initially used for? a piece of classic music, a theatrical piece, a book, or what?