Pâté de Foie Gras; Foie Gras D’oie and Foie Gras De Canard
The original and classic foie gras is made from goose liver, and the technique dates back at least 4,600 years to the 4th and 5th Egyptian dynasties. There are paintings in tombs from that period which show geese being held by the neck and being feed balls of grain. This is called 'gavage' and the method is basically unchanged today.
The theory is that an Egyptian farmer had a goose that had an abnormal appetite, and gorged itself on grain. When it was killed for its meat, it was notice that the bird had an oversized liver that was delicious. We know for sure that by 50 B.C. the Romans were force feeding geese figs, and soon after were using the same method with ducks and even pigs.
Generally the term foie gras is used for goose liver, although it is also used to refer to duck liver. Goose liver is considered superior by most people.