Swanning is a term for dying. Originally, it only meant twisting yourself in your sheets while asleep and strangling to death. Now it can also mean having swans wrap their necks around you, drag you out into the water to drown, and then using your hair for a nest.
I've had such a bad day at work, I really feel like swanning
Essentially this is a variation of "the Shocker." Swanning occurs when a person places either the pinky and or ring finger into a womans anus while reaching the thumb over the vagina to apply clitoral stimulation. One can imagine the position and reaching of the thumb as the craning of a swans neck.
Woman: My vagina is so sore right now, but I'm kinda horny. Could go for a serious Swanning right now.