Nowadays, the word "spoilers" is frequently used to describe a twist, major plot point, or anything which, if known beforehand, might spoil the experience of reading a story. This whole concept hasn't always been much of a thing, and I'd assume that the word "spoiler" itself in this meaning is an even more recent invention. EtymOnline says this meaning of the word "spoiler" goes back to (at least?) 1982, but it doesn't provide any citation for this claim nor say where "spoiler" was used in 1982.
When and where was the term "spoiler" in this meaning first used/introduced?
Not a duplicate of History of Spoilers which is about the history of the concept; this question is about the history of the term.