Wool is the soft, thick, curly hair that grows on sheep and some other animals like goats and alpacas. For thousands of years, people have sheared this hair from animals (cutting it off without hurting them when done properly), then spun it into yarn and woven it into fabric. Wool makes excellent clothing because it keeps you warm even when it gets wet, unlike cotton, which can feel cold and clammy when damp.

Sheep grow a new coat every year, so farmers shear them each spring before the weather gets too hot. A single sheep can produce enough wool for several sweaters. The fibers have natural oils that repel water and make wool somewhat self-cleaning. That's why wool coats, scarves, and blankets work so well in cold, wet weather.

When people talk about pulling the wool over someone's eyes, they mean tricking or deceiving them. Today, if a salesperson tries to pull the wool over your eyes, they're trying to fool you about what they're selling.