Toons actually originated from UO...So, the "meaning" attached to the word has existed longer than most of FFXIV's audience has been alive...Thus, it more than likely will exist far beyond the scope of the game.
It also existed earlier in the FF series, particularly FFII and FFIII...
I don't understand why it's a big deal, really. In the early days of UO, your characters looked like cartoons, thus they were called Toons.
We're willing to modify the Oxford dictionary for "Yolo" and "Twerking" yet, none of you can accept the use of a term that's existed since the 90s - Interesting.