Days of the Week

[Lionel Mandrake]

5. The relationship between "month" and "moon" is clear.

Wiktionary gives the following etymology of "month":

From Middle English month, moneth, from Old English mōnaþ (“month”), from Proto-Germanic *mēnōþs (“month”), from Proto-Indo-European *mḗh₁n̥s (“moon, month”), probably from Proto-Indo-European *meh₁- (“to measure”), referring to the moon's phases as the measure of time, equivalent to moon +‎ -th. Cognate with Scots moneth (“month”); North Frisian muunt (“month”); Saterland Frisian Mound (“month”), Dutch maand (“month”); German Low German Maand, Monat (“month”); German Monat (“month”); Danish and Norwegian Bokmål måned (“month”); Norwegian Nynorsk and Swedish månad (“month”); Icelandic mánuði (“month”); Latin mēnsis (“month”); Ancient Greek μήν (mḗn); Armenian ամիս (amis); Old Irish mí; Old Church Slavonic мѣсѧць (měsęcĭ . See also moon.

And of course the plural of the Latin mēnsis (“month”) is mēnsēs (“months”), from which the English words "menses", "menstrual", etc. are derived (you alluded to this).