Tansy is a wild flower, native to Europe and Asia, but introduced to America and elsewhere.
So why would anyone introduce a wild flower into their homeland? Isn't a wild flower just a weed that's been noticed by a poet?
Well, tansy is useful stuff. It's said to be good for killing intestinal worms and preventing flatulence (especially valuable during Lent, apparently, when people aren't allowed meat and so tend to fill up with beans). Putting some in your bath water is said to cure joint pain, and it's still approved in the USA for treating fevers and colds.
Tansy is a good insect repellent, too, and has been rubbed on meat for this purpose (not recommended, as tansy can be poisonous) and also used at funerals (eerrgghh). If you plant tansy with potatoes then Colorado beetles tend to turn up their noses (proboscides?) and go elsewhere, and if you wear it round your neck then mosquitoes tend to bite someone else.
You can make omelettes with tansy (if you're prepared to risk being poisoned) and tansy sweets might even help your gout.
But the best reason to use the word tansy is because it is a word that dances.
Quite possibly the can-can if you try eating it.
Word To Use Today: tansy. This word comes from the Mediaeval Latin athanasia, from the Greek word meaning immortality, because it was believed to prolong life.
So now you know why there are no Ancient Greeks left around.