You can learn a lot about yarrow from its Latin name, Achillea millefolium. The Greek warrior Achilles is said to have carried yarrow into battle to use as a way to staunch blood from wounds. And just as the word millefolium suggests the tightly-clumped inflorescences, it's also appropriate considering its manifold medicinal uses, from the stomach to the respiratory system to the liver. A strong name befitting a strong plant: it is pest and drought resistant and will spread eagerly if allowed.