The History of “Personalized Learning” [...]

What is the history of "personalized learning"? (When did it change from being "individualized learning," for example?)

According to Wikipedia, the term dates from the 1960s. But Google's Ngram Viewer shows it was in use prior to that.

Was the bump in the 1970s due to the commercialization of early teaching machines? And similarly, was the increase in the late 1990s onward a result of computer-based instruction? Or was this the influence of the Gates Foundation? (Or both?)