means To gradually decrease in size, strength, intensity, or power — to diminish over time, the way the moon shrinks from full to dark.

from From Old English 'wanian,' meaning to lessen or dwindle, rooted in a Germanic source tied to the sense of being deficient or lacking. It shares deep ancestry with 'want' and 'wanting' — all circling the idea of something growing emptier. For centuries it has clung especially to the moon, whose monthly shrinking gave English its most familiar picture of decline.