I don't just mean the word specifically. The CM at Epcot guest services clearly understood what I was expecting to happen, but they were adamant that you had to pay the full price difference between the discounted price paid at UCT and the current AP price. You need to be prepared for resistance and possibly walk away if the CM is that badly trained.
I believe the first time I saw the term was when it was used by Cheshire Figment a decade or so ago in drafting a Ticket FAQ on the Disboards based on his actual experience as a CM at WDW. So it's pretty likely that he got the term itself from Disney.
At any rate, if you check google, the term is used by Touring Plans, Mousesavers, TripAdvisor, ThePointsGuy, Reddit, EasyWDW and Pinterest among many others. If it used to be an obscure, niche practice taught on the Disboards, it's fairly widely discussed now.