The central point of a wheel, or more broadly, the most important central place where activity and connections happen.
From Middle English and Old English, possibly from a Proto-Germanic root related to 'to hump' or 'to swell.' The center of a wheel naturally swells outward where the spokes connect.
Hub is a perfect example of how a physical object's name becomes a metaphor—ancient chariot wheels had a center point, and now we talk about 'social hubs' and 'transportation hubs' to mean central gathering places. Our brains constantly borrow words from concrete things to describe abstract ideas.
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