Fred is not an official Google update: Google never confirmed it. Around March 8, 2017, rank trackers and site owners reported major ranking volatility, and Search Engine Land covered it as a new, unconfirmed ranking update, noting that early chatter, much of it from the black-hat SEO community, suspected changes around link quality. Google offered only its stock response that it makes updates regularly.
The name was an accident of humor. Google's Gary Illyes joked on March 9, 2017 that "from now on every update, unless otherwise stated, shall be called Fred", per Search Engine Journal's history of the update, and the community adopted the name for this one. The most-cited characterization also comes from the community: Barry Schwartz reviewed more than 100 affected sites for Search Engine Land and found roughly 95% were ad-heavy, low-value-content sites that put revenue above helping users, with reported organic traffic drops of 50-90%.
Google declined to describe the update at all. At SMX West later that month, Illyes said Google's search leads had decided not to talk about Fred, saying only that the techniques it affected were "well-documented within the Google webmaster guidelines", without specifying which. Because the update was never confirmed, there is no official target and no official recovery path; everything written about Fred rests on community analysis of the coverage cited here.