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How does the name yahoo from Gulliver’s Travels came to describe a crass or foolish person?

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Illustration of Lemuel Gulliver lying on the ground, tied down by tiny Lilliputians, with crowds and small buildings in the background, from Jonathan Swift's Gulliver's Travels. — Gulliver’s Travels Lemuel Gulliver in Lilliput, illustration from an edition of Jonathan Swift's *Gulliver's Travels*.

In Jonathan Swift’s 1726 novel Gulliver’s Travels, the term "Yahoo" was invented to describe a race of brutish, humanoid creatures encountered by the narrator, Lemuel Gulliver, on his fourth voyage.12

These Yahoos are depicted as filthy, greedy, and selfish beings who possess the physical form and vices of humans. In the narrative, they are contrasted with the Houyhnhnms, a race of highly intelligent, rational, and benevolent horses. Because the Yahoos represented Swift’s satirical view of humankind at its most base and degenerate level, the term naturally transitioned into the English language as a descriptor for a person who is particularly boorish, crass, or unintelligent.123

Essentially, applying the label "yahoo" to a person today serves as a direct reference to the characterization of these creatures as the embodiment of human flaws and lack of reason.13