Question for my social activist flisties

When did the term "privilege" (with respect to *isms) come into popular use? I personally first heard it on the internet through BtVS fandom, so less than 3 years ago (and have never heard anyone use it in real life), but y'know, I'm slow. Anyone know when it started being used?

The reason I ask is because I'm reading this article for class, which is basically about how white privilege and economic privilege make certain groups "politically invisible," except it never actually uses the word "privilege," and I'm sure it was written way before that became common terminology, but it made me curious as to when that actually happened.