Store the head, unwashed, in a plastic bag in the fridge. Or wrap a damp paper towel around the head and place in the crisper. These should last 4-5 days (or more) when properly stored.

British folks tend to call it "Cos" lettuce becuase it is said to have originated on the Greek island of Cos (Kos) near Turkey.

Romans usually ated it cooked as Cappadocian lettuce and was also called Roman lettuce because of their belief in its healing properties. According to the Roman historian Pliny, Augustus Caesar put up a statue to honor it after being cured of a serious illness believing in its healing abilities.

The Popes in the 14th Century brought this lettuce with them when they temporarily moved from Rome to Avignon and called that name as well.