Barley is a cereal plant grown for its grain. People cook the grain in soup — pearl barley is the grain rubbed until it looks like little pearls — and they malt it to make beer and whisky. Barley water is an old, mild drink. The plant looks a little like wheat, though actually the head often has long bristles, and the jobs are different: wheat for most bread, barley for beer, whisky, and some stews. It copes well with cool, rough weather, so northern farms have grown it for a very long time. The word is ordinary farm-and-food English, not fancy.