XO means extra old to classify the cognac. According to the Bureau Interprofessionel du Cognac, these are the classification of cognac:
1. VS (very special)
2. VSOP (very superior old pale)
3. XO (extra old)
4. XXO (extra extra old)
5. Hors d'age (beyond age)
This is maybe the reason why this type of durian is named XO(extra old) because of the similarities taste with the cognac bitter taste.