Tyranny of the majority is a phrase that both critiques and promoters of democracy use. It has the potential to be its greatest weakness. Tyranny of the majority means that the crowds lay their interest above the interest of the minorities.
It is unknown who exactly came up with the phrase. The fear was present already in Ancient Greece and Rome. However, some of the Founding Fathers of the USA generally claim the attribute for it. That makes sense.
The late 18th century marked the time when modern democracies began to emerge. Political philosophers at the time were uncertain, whether particularly the broader group of the less wealthy, would not abuse democracy in their favor. More importantly, the general understanding of democracy at the time was the direct form. That is in contrast to today. Now, it is the representative form.
In summary, the majority can be mistaken. It can do wrong things and make bad decisions. And that is a problem.
James Madison is one of those who warned of this feature in Federalist 10. Madison expects that checks and balances along with other institutions and the separation of power can prevent it. Further, the second president of the USA, John Adams, believed that Americans would abuse a unicameral government by the logic of tyranny of the majority. That is why the USA is bicameral – with the House of Representatives and the Senate.
It was not merely an American problem. European scholars addressed the topic as well. In Democracy in America, the Frenchman Tocqueville says that democracy can lack social hierarchy. Thus, it can compromise the rights of individuals. He thinks Americans see the majority as faultlessness. In the same way, the French view the monarchy.
John Stuart Mill built on the ideas of Tocqueville. In his On Liberty, he says that individual rights have to be independent of the government. It can abuse people’s rights based on what the majority might want. Besides, he remarks that the pressure of public opinion on an individual is also the tyranny of the majority.