xkcd #3232: Countdown Standard
Title text:
Anyone who is caught counting 'three ... two ... one ... zero ... GO!' will be punished with a lifetime of eating only ISO standard food samples.
Transcript:
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Source: https://xkcd.com/3232/
Fortnightly already exists as a term though, why would biweekly mean the same thing?
We can have more than one way of describing things. Sometimes there is subtle nuances between the words.
No one ever uses fortnightly though. I have a hard time even remembering what it means as it's never used.
Americans never use fortnight. I suspect this is because very few get to enjoy 2 weeks of uninterrupted vacation.