Lambswool is the soft wool that comes from a lamb, used for jumpers, hats, and other warm clothes. It feels finer and kinder on the skin than wool from an older sheep, which is why clothes labels like the word. It is often written as one word on a tag. Though actually, in older British English lambswool (or lamb’s wool) was also a hot drink of ale with roasted apples and spices; people said the foam on top looked like wool. You will almost always meet the clothing sense now. It names the material, not a whole animal.