Pompoir is vaginal and pelvic muscle strength and control. It would take about 30 seconds to look this up on Wikipedia, for a much better explanation.
There have been a few pompoir experts I’ve met over the years at MPs, often average-looking girls in their early 30s who you wouldn’t expect to have some kind of miraculous skill. It seems like a talent not necessarily associated with being petite or athletic etc. Anyway, I wish that people with this talent would advertise it. It is also a trainable skill using Kegel exercises etc.