Vrftjkry

I have seen on Facebook, a post (in French) claiming that many words for the night are based on a n+respective number for the number 8. For example on this website,

Language      Number 8  night

français        huit    nuit 

anglais         eight   night 

allemand        acht    nacht

espagnol        ocho    noche 

portugais       oito    noite

italien         otto    notte

néerlandais     acht    nacht

suédois         aetta   natta 

roumain         opt     noapte

wallon          ût      nut 

occitan         uèch    nuèch 

catalan         vuit    nit 

gascon          ueit    nueit 

picard          uit     nuit 

piedmontais     eut     neuit 

espéranto       ok      nokto

The post goes even further, claiming that N is a symbol for infinity, and that 8 is the typical infinity symbol rotated.

My first reaction was to dismiss it. But then, I've been thinking about it, and would really like to have reasons to dismiss it.

The infinity symbol dates from 1655 (according to Wikipedia)whereas the word nuit was already in use by 1170 (website in French). Furthermore, the word nuit was used as noit in older French, and derives from noctum (latin) and thus nox (littré in French). But unfortunately, my knowledge of Latin is by far too limited to investigate further on the Latin.

Actually, the last link mentions that for the author M. Ad. Regnier, studying the Sanskrit, it could be related to the word naked (German: nackt, Latin: nuda).

In English, (the ight deriving from eight sounds worse than some other examples), what I gather is that

Old English niht (West Saxon neaht, Anglian næht, neht) "night, darkness [...] from Proto-Germanic *nahts

which relate as well to nox (Latin), nuks (Old Greek) or naktam (Sanskrit). The same website also indicates that

according to Watkins, probably from a verbal root *neg- "to be dark, be night."

But, if the relation night -> infinity -> infinity symbol -> 8 -> night, sounds improbable, I cannot find definitive information on a possible relation between the number 8 and the night.

Can you help me get down to the bottom of that question?

No, they are unrelated.

Some Proto-Indo-European language (PIE) reconstructions from Wiktionary:

• "eight": "oḱtṓw" (claimed to be a dual of "four fingers")


• "night": "nókʷts" (possibly from "bare, naked").

As @Schmuddi mentioned in a comment above, it looks just like a coincidence (slightly similar proto-language words). The rest looks like an urban legend.

Sources:

• McPherson, Fiona. Indo-European Cognate Dictionary. Wayz Press, 2018. (Google Books link)

• Watkins, Calvert. The American Heritage Dictionary of Indo-European Roots. Houghton Mifflin, 2000. (Google Books link)

In English "eight" and "night" came from different words, "ehte" and "niht" respectively, which have both undergone a common substitution of -gh- for a hard "h", which was a Middle English scribal habit.

In French, "huit" came from "uit" when an "h" was added to avoid confusion with "vit". As for "nuit", it's a transformation of old French "nuict" derived from latin "noctem", which is an inclination of "nox".

The etymological link can be tracked further down, but the two words remain distinct, albeit similar.

So at least for English and French, the similarity between these two words is not due to a common root, but rather to similar ancestor words, and in some cases common transformations which contributed to the similarity of modern forms. I don't know other languages in your list, but they all seem to be either Latin or Germanic, so they likely share their etymological transformation with French and English respectively.

No, night and day come from old Norse.

https://glosbe.com/en/non/night

nátt { noun feminine }
The period between sunset and sunrise, when a location faces far away from the sun, thus when the sky is dark.

https://en.wikipedia.org/wiki/N%C3%B3tt

In Norse mythology, Nótt (Old Norse "night"[1]) is night personified, grandmother of Thor.

https://en.wikipedia.org/wiki/Dagr

In Norse mythology, Dagr (Old Norse "day"[1]) is day personified.

Old Norse blended with early Germanic languages, from which English is derived.