Plural of backbone; the series of bones running down the center of the back (spine), or it can mean the main support structure or strongest part of something.
Old English 'bæcbān' (back bone). The metaphorical sense of 'main support' or 'core strength' developed by the 1600s as people began using physical backbone to describe essential strength in systems or character.
The spine is literally made of 33 individual bones stacked like a tower, yet we treat it as one unit called the 'backbone'—and that's exactly how organizations work: many people creating one unified strength.
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