I initially thought this was recent and it's crazy that the "fake news" idea have stuck around now for 6 years.
In the 1980s, "fake news" referred to pre-canned "news" segments created by commercial interests (or their trade organisations) as "video news releases" (VNR) or "audio news releases" (ANR).
That was the context in which the phrase "fake news" was being discussed as recently as 2007/8.
<https://www.sourcewatch.org/index.php?title=Fake_news>
Jim Cameron, "PR & Media: The Perfect Ethical Storm" O'Dwyers PR Daily, June 2, 2005. <http://www.odwyerspr.com/members/0601comm_cameron.htm>
Brooks Boliek, "FCC urges fine for Comcast: VNR was aired as part of newscast," Hollywood Reporter, September 25, 2007. <http://www.hollywoodreporter.com/hr/content_display/televisi...>
(Many more references at the SourceWatch article above.)