wax and wane

Referring to the phases of the Moon (about 14th century). (Compare wax with the German cognate wachsen (“grow”).) By folk etymology, this verb phrase has occasionally been mistakenly presumed to be a reference to candles, under the notion that waxing of a wick (applying wax) produces a candle that, once lit, immediately begins to wane away until complete darkness.

wax and wane (third-person singular simple present waxes and wanes, present participle waxing and waning, simple past and past participle waxed and waned)

1. To progress cyclically through various phases, such as growth and senescence.
2. To alternate; to increase and diminish in turn.

   The manifestation of such philosophy seemed to wax and wane, being the most common one time, but virtually without followers at another, apparently disappearing.

• ebb and flow (verb) (especially when used figuratively)