Many years ago it was permissible to hunt swans for food, but only on certain days that were declared by the King or Queen at that time
These days were rare in the calendar, so many people took time off work to join in the hunt. The numbers caught were strictly controlled enabling the Swans long term survival. So even in those medieval days we were conservationists
Now of course the hunting of swans is forbidden, many die through lead poisoning caused by fishermen and the lead weights that they use and leave behind, but they survive in most of our waterways and have been known to drown any passing dog that threatens their cygnets
So even today if someone takes time off work without a proper reason they are referred to as "Swanning Off" as in the expression "Where are you Swanning off to?"
The younger generation use this term but unfortunately most do not understand its origin
Not a lot of people knows that.... as Michael Caine would say