When and how did the term "MSM" become mainstream?

On Twitter, in recent months, MSM for "mainstream media" has become a standard term. Yet when and how did that term appear, more regularly? A search under "Wonks" can give you a quick overview.

Again, if you want the most recent results, toggle between relevance and date. This is just one of many searches you can undertake. Interested in views in Russia, Turkey or Indonesia? All of that is available, too. Try a search under Wonks or More.