According to wikipedia Nick Pelling coined the term "Gamification" in 2002/2003 as part of his bussiness model Conundra.
Though the term "gamification" was coined in 2002 by Nick Pelling, a British-born computer programmer and inventor, it did not gain popularity until 2010.
Reading further gives me some skepticism...
Even prior to the term coming into use, other fields borrowing elements from videogames was common; for example, some work in learning disabilities and scientific visualization adapted elements from videogames.
And above all Yu-kai Chou claims
In short, I’m the creator of the Octalysis Framework (internationally recognized Gamification Framework)
According to a TED video posted in 2014, Yu-kai Chou was researching gamification for about 13 years...that's 2001.