the.com/brood

Either your children or your sulking — nature's way of linking the two.

means To brood is to sit heavily on anxious or resentful thoughts, turning them over again and again, the way a hen sits unmoving on her eggs.

from From Old English 'brod', meaning offspring or the act of incubating eggs, itself from a Germanic root tied to warmth and hatching. The literal sense — a bird sitting patiently on her clutch — gave rise by the 1500s to the figurative one: a mind sitting just as fixedly on a dark or worrying thought, refusing to let it hatch or go cold.

origin
old english for fetus, same root as breed
collective noun
a brood of chickens, specifically
verb form
sitting on eggs became sitting on grudges
peak usage
teenagers and hens, oddly similar behavior
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