This is one of my weirder little fantasies. Sorry to go on about it, but when I'm on a swing (which I often am, a) because I like it and b) I have a child who's still young enough to like it, so I have a valid excuse) I always think spanky things.
Not sure why. I think it's about the way your bottom sticks out in a distinctly inviting way why you really get going on a swing.
It seems to me that anyone with even a hint of the spanko about them who's standing behind me must have an inclination to smack. There (in my case) is one curvy and rather big bottom hurtling at them that is just begging for a good, meaty spank.
If roles were reversed I don't think I could resist. Anyway, I happened upon this image today and that got me thinking about the swing-spanking equation again. In this case the position isn't quite right but the basics are there:
Swing + Instrument of Correction = Ouch