The spine or vertebral column of a skeleton; also used metaphorically to mean courage, determination, or the most important supporting structure of something.
A compound word combining 'back' and 'bone.' Originally referred literally to the spinal column, then metaphorically to moral strength and core structure.
Your backbone is so important to your biology that every vertebrate animal has one—that's why fish, reptiles, birds, and mammals are all called 'vertebrates,' and the backbone is what defines this huge group of animals!
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