Since the 1980s.
"A
strategic lawsuit against public participation (SLAPP) is a lawsuit that is intended to censor, intimidate, and silence critics by burdening them with the cost of a legal defense until they abandon their criticism or opposition.[1] Such lawsuits have been made illegal in many jurisdictions on the grounds that they impede freedom of speech.
"The typical SLAPP plaintiff does not normally expect to win the lawsuit. The plaintiff's goals are accomplished if the defendant succumbs to fear, intimidation, mounting legal costs, or simple exhaustion and abandons the criticism. In some cases, repeated frivolous litigation against a defendant may raise the cost of directors and officers liability insurance for that party, interfering with an organization's ability to operate.[2] A SLAPP may also intimidate others from participating in the debate. A SLAPP is often preceded by a legal threat.
...
"The acronym was
coined in the 1980s by University of Denver professors Penelope Canan and George W. Pring.[5] The term was originally defined as "a lawsuit involving communications made to influence a governmental action or outcome, which resulted in a civil complaint or counterclaim filed against nongovernment individuals or organizations on a substantive issue of some public interest or social significance." The concept's originators later dropped the notion that government contact had to be about a public issue to be protected by the Right to Petition the Government, as provided in the First Amendment. It has since been defined less broadly by some states, and more broadly in one state (California) where it includes suits about speech on any public issue.[6]"
From
https://en.wikipedia.org/wiki/Strategic_lawsuit_against_public_participation(My emphasis - more @ the URL)
So, these have been around for 35 years or so. A whole generation, @ least.