From The Food Encyclopedia by Jacques Rolland and Carol Sherman
Also cobnut, filbert. A fruit of the hazel tree of the genus Corylus. The most important variety of hazelnut is the Barcelona, introduced in the U.S. in 1885; it is the most extensively grown variety there. The nuts are large, thick-shelled, round and broad-shouldered, with a blunt point and a rich chestnut-brown color. The name "filbert", Corylus avellana, most often used in England for a cultivated hazelnut, takes its name from St. Philibert, a 7th-century Frankish abbot whose feast day on August 22 coincides with the nuts' ripening time. Native to the Mediterranean region but now grown all over Europe, hazelnuts can be eaten on their own or used in desserts and confectionery.
