How is there a fourth half? That doesn't make any sense mathematically.
Clearly you're not giving it 200%
Also de derde helft is commonly used for the time spent in the sports canteen (usually drinking beer) after playing a football or hockey match (hockey = field hockey in the Netherlands).
You can have four times 50% of something.
From American Football, maybe?
Guys, imagine some $1/2 American coins. I love collecting them.
This lesson was brought to you by Fifth Third Bank.
I also agree that 'vierde helft' sounds weird. I typed 'vierde gedeelte' but it was incorrect.