Supporting and cheering for someone, like 'rooting for' a team; also the act of digging around searching for something.
From Old English wrōtan, meaning to grub or dig. The 'supporting' sense came later, possibly from the image of animals rooting around to find what they want.
When you're 'rooting for' someone, you're actually using an animal metaphor without realizing it—you're described as digging and searching for their success the way a pig roots for truffles in the ground.
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