The original meaning of the word month?

Answer 1

The term 'month' comes from Middle English moneth; which comes from the Old English term 'monath'. Additionally it is akin to Old High German manod meaning month and Old English Mona, meaning moon. It in all probability is related to mê, an Indo-European term (meaning to measure), actually referring to the various moon's phases used as the measure of time.

Answer 2

Most likely "month" is a corruption of the Middle English word "moneth": itself a corruption of the Old English "monath". In general, all these words are supposed to refer to the Moon.

The original idea was that months would coincide with lunar cycles (new moons, full moons, etc.). It made for a handy reference that didn't take too long to sync.

They don't exactly line up now because astronomers came to realize that the lunar orbit cycle and the Earth's orbit cycle don't line up (they're off by a margin of about 11 days). Since it's the Earth cycle that causes the seasons, it was considered more important to line up the year to the Earth cycle than the month to the lunar cycle. Though calendars have changed over the centuries, the idea of using the lunar cycle (about 28 days) as a rough baseline for the length of a month has stuck with the modern Gregorian calendar.

Just for reference, the Gregorian interpretation is not universal. The Hebrew calendar, for example, doesn't use 31-day months and thus sticks closer to the original lunar concept of the month. Probably the calendar most adherent to the original lunar concept of the month (in widespread use) is the Chinese calendar.