Increase and decrease, as in size, number, strength, or intensity, as in Enrollments in these programs wax and wane from year to year. This expression alludes to the phases of the moon, with its periodic changes in size. It was first recorded in the 1300s.
American Heritage Idioms
Phrase(s): wax and wane
Fig. to increase and then decrease, as the phases of the moon. • As the moon waxes and wanes, so does the height of the tide change. • Voter sentiment about the tax proposal waxes and wanes with each passing day.
McGrawhill's American Idioms And Phrasal Verbs