A flu-flu...well, it's going to be something ridiculous, isn't it, like a poodle's hair-cut, or the feeling of panic you get when you open your wallet and discover your credit card isn't in its usual slot.
But it's nothing like that. A flu-flu is an agent of death.
Here's its tail:
Can you guess what it is?
It's the curled and cut (usually turkey) feathers on an arrow. They're treated in this way to reduce the arrow's range.
This sort of arrow has a blunt tip, so it will kill small animals and birds, but is unlikely to plunge itself inconveniently into the ground or a tree.
Flu-flu arrows might be bad for birds, but they've saved quite a lot of human lives. You see, in England in the Middle Ages you were allowed to shoot birds anywhere, but if you were caught on someone else's land with a sharp arrow suitable for killing deer then you'd probably be executed.
Flu-flu arrows are used by children, and also in flu-flu golf, where you keep shooting from the place your last shot landed until you reach your target.
Honestly, flu-flu golf...
...it still sounds like something you'd play accompanied by a lilac poodle, doesn't it.
Word Not To Use Today: flu-flu. I can't find any information at all about the derivation of this word. I suppose it must have been made up by an archer. The mind boggles.