This abbreviation means "I Want You To Fuck MeSo Hard I Can't Walk Anymore"
Example
Boy 1: Hey Jess, if you're a freak, then you know what I.W.Y.T.F.M.S.H.I.C.W.A
Jess: Yeah, I know what it means. I'm not that innocent. "I Want You To Fuck Me So Hard I Can't Walk Anymore"
Brought to public attention by Bob Woodward and Carl Bernstein in the book on the fall of Richard Nixon, All The President’s Men, ratfucker was Nixon’s term for a political operative who sows chaos among opponents; an agent provocateur. It is thought to have originated among campus political rivalries at USC, and seems to have some usage in the US military.
Along with Nixon’s other ratfuckers, Roger Stone caused fights at otherwise peaceful Democratic Party protests to generate a false narrative that the Democrats were violent and dangerous.