Calabria - The region where the Esrogim grow
The Calabria Esrogim originate from the homonymous region located in the southern part of Italy. These Esrogim grow on a strip of land on the coast also called "Riviera dei Cedri".
They are also called Yanover Esrogim for the city of Genova, in the north, from where they were shipped in the past.
Others refer to them as Italian Esrogim since it’s believed that in the past they also grew in other parts of Italy.
The tradition of the Calabria Esrogim
The Alter Rebbe transmitted a tradition: When Hashem commanded the Jews in the desert to take an Esrog, he sent messengers on a cloud and they brought him the Esrogim from Calabria.
Since then the Minhag of the Rabbeim, and therefore of the Chabad Chassidim, is to make a Brocha on an Esrog from Calabria.
Why is Calabria so special?
The Rebbe also said that the south of Italy is called Magna Graecia or איטליה של יון . The Medrash Rabba and Rashi also quotes it, saying that the posuk “משמני הארץ יהיה מושבך” refers to Magna Grecia and since we have to take the best for our service to Hashem, the ideal is to take Esrogim from Calabria”.
The Rabbeim always tried to use an Esrog from Calabria. One year, when the Frierdiker Rebbe didn’t receive an Esrog from Calabria because of the war, it is recounted that he had fever, his Holy face was swollen and he didn’t come out to daven the first days of Sukkot. Another year when it happened again it's recounted that he cried at length.