The late and great Patrick Winston who is probably best known for being a professor at MIT tought a class (or gave a lecture at least) about how to speak.
Some of these has been recorded, and I just finished one. (Someone shared it on hackernews not long ago, but I never got around to see it)
I find it to be a must-see for anyone doing any sort of presentations for other people. (And don’t we all end up doing that at some point?)