Paralipsis (https://en.wikipedia.org/wiki/Paralipsis https://en.wikipedia.org/wiki/Paralipsis), or parasiopesis or præteritio as it was called when I was in sch

Paralipsis (https://en.wikipedia.org/wiki/Paralipsis https://en.wikipedia.org/wiki/Paralipsis), or parasiopesis or præteritio as it was called when I was in school, means something very like what you describe.