Why is the word "democracy" not in the preamble of the US Constitution?

Why? Try these on for size:

Another tendency, which is extremely natural to democratic nations and extremely dangerous, is that which leads them to despise and undervalue the rights of private persons.

To Indians: “Pack up what belongings you can carry and start walking to Oklahoma. Your fertile lands are ours now. We voted fair and square and your side lost.”

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The republican is the only form of government which is not eternally at open or secret war with the rights of mankind.

To blacks: “You can’t drink from that water fountain… eat in this cafeteria… ride this bus… go to this school. We voted fair and square and your side lost.

—John Adams

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[with republicanism being the rights-protecting form of governance afforded us by our Constitution]

—Benjamin Franklin

To slaves: “You can forget your notions of freedom. We voted fair and square and your side lost.”

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When the people find they can vote themselves money, that will herald the end of the republic.

—Thomas Jefferson

—Alexis de Tocqueville

🔥Why has Prime Narendra Modi become Extremely FRUSTRATED and Highly DEPRESSED because he has NOT been invited by Donald Trump to witness his Oath Ceremony for his INAUGURATION on 20th January as the next PRESIDENT of USA? Does the DESPERATE Narendra Modi FEAR that Donald Trump's actions may even LEAD to the FALL of the BJP-led MINORITY Government in India, as such actions have already caused GREAT PANIC in the NDA Coalition?

Meanwhile, when the Democratic Party formed in 1828, it was with a Tory outlook keen on robbing others of their rights:

I do not say that democracy has been more pernicious on the whole, and in the long run, than monarchy or aristocracy. Democracy has never been and never can be so durable as aristocracy or monarchy; but while it lasts, it is more bloody than either.

In other words, our Founding Fathers and other Whig intellects of that time well understood that democratic methods are the surefire means to do serious damage to the rights guaranteed under republican self-government.

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Majority-rules democracy is the way that majorities run roughshod over minorities, destroying rights and all ideas of equality under the law. No fair-minded person wants anything to do with democracy.