X.O. (Old Extra)
XO stands for Extra Old and it describes a Cognac consisting of eaux-de-vie that have been aged in oak barrels for a minimum of six years. However, XOs often have a much older average age, with many XO Cognacs being 20 years old and older.
The expression XO was used for the first time in 1870. An XO Cognac can also be called “Napoleon” or “Old Reserve.”