Why is Northern Ireland called Ulster?

Related questions

1. Is North Dublin safe?
2. Are there trams in Dublin?
3. Where do Saracens train?
4. What Luas goes to the 3 Arena?
5. How much did the Luas cost?
6. Does the Luas run all night?
7. What time does the Luas stop running at night?
8. What road is the RDS on?
9. Why is it called the o3 arena?
10. What does the RDS in Dublin stand for?

Tags

1. #northern
2. #other
3. #cavan
4. #partitioned
5. #became
6. #ulster
7. #country
8. #three
9. #provinces
10. #formed
11. #states
12. #state
13. #known
14. #monaghan
15. #ireland
16. #donegal
17. #twenty
18. #counties
19. #remaining