wax and wane

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

Verb

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