On the Fact that Only 3% of Hispanics Refer to Themselves as Latinx (with 76% Never Having Heard the Silly Made-Up Word Before) - Numbers from Pew Research

Not certain about the word's origin but if I had to guess I'd likely wager that it came from a small group of insular, lightweight, and white-as-eggshell "academics" whose genius idea was hatched about as far from the barrio as Venus is from Jupiter. Just like a lot of other shit (restorative justice, psycho-educational learning, anti-racism, gender non-binary, etc., etc.).