https://en.wikipedia.org/wiki/Conspiracy_theory#Origin_and_U...
> The earliest known usage was by the American author Charles Astor Bristed, in a letter to the editor published in The New York Times on January 11, 1863.
> The term "conspiracy theory" is itself the subject of a conspiracy theory, which posits that the term was popularized by the CIA in order to discredit conspiratorial believers, particularly critics of the Warren Commission, by making them a target of ridicule.
Who popularized it is subjective.
What isn't subjective: the CIA indeed sent out a memo about this. It marked an increase in the use of the term in popular media publications. You can find it and read it.
> the CIA indeed sent out a memo about this
Wow, the CIA noticed something and sent a memo?
AT&T is almost certainly not storing every text message long-term. The NSA likely is. It wouldn't be surprising if that's via a direct PRISM-style integration, but it still means subpoenaing AT&T for old texts is likely to not be productive. (As it was not productive in this particular case.)
Subpoena the NSA and they'll say "no, for national security reasons".
6 billion text messages are sent per day in the US. That's about the volume of Google web searches, and I know from experience Google doesn't have the capacity to log every search or the logs of evaluation of every search. If Google lacks the capacity, I suspect the NSA lacks the capacity.