A small, round bread roll, often slightly sweet; also a hairstyle where hair is twisted and coiled into a round shape on the head.
From Old French 'bugne' (swelling or bump), ultimately of uncertain origin. The hair meaning came later by analogy—the coiled hair resembles the coiled bread.
The word 'bun' is wonderfully dual—it's both food and fashion—and both meanings came about because of shape similarity. This shows how humans understand the world metaphorically: we call a hairstyle 'bun' because it looks like the thing we eat.
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