Do we know why? Is (was) 8:00 the standard for “night”? How long has the day been around? Was it 8 hours from sunrise?!? Well, I added nothing to this post...
I'm fairly certain it is largely a coincidence
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The etymology shows the root words have very little in common, but a lot of languages share the same root origin for their words, so the coincidence carried across multiple languages
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The etymology shows the root words have very little in common, but a lot of languages share the same root origin for their words, so the coincidence carried across multiple languages