Short answers, pulled from the story.
Antoine Destutt de Tracy, a French Enlightenment aristocrat and philosopher who lived from 1754 to 1836, coined the term in 1796 as a science of ideas. He developed it while imprisoned from November 1793 to October 1794 during the Reign of Terror, reading Locke and Etienne Bonnot de Condillac.
An ideology is a set of beliefs or values attributed to a person or group, especially those held for reasons that are not purely about belief in certain knowledge. Recent analysis treats it as a coherent system of ideas resting on a few basic assumptions about reality.
Napoleon Bonaparte, who lived from 1769 to 1821, turned ideology into a term of abuse by hurling it at his liberal foes and describing his opponents as the ideologues. Karl Marx later adopted Napoleon's negative sense, and an ideologue today often means someone blindly partisan, zealous, or fanatical.
Marx saw ideology as a system of consciousness arising from economic relationships that reflects and perpetuates the interests of the dominant class. In his base and superstructure model, the economic base determines the political superstructure, and ideology produces a false consciousness that leads exploited groups to support a system against their interests.
Eric Hoffer identified hatred, imitation, persuasion, coercion, leadership, action, and suspicion as the elements that unify followers of an ideology. He wrote that mass movements can rise and spread without a God but never without belief in a devil.
The World Values Survey, built by Ronald Inglehart of the University of Michigan and running since 1980, has mapped attitudes in 100 countries representing 90 percent of the global population. It found that where people live closely correlates with their ideological beliefs, with Protestant Europe leaning secular and liberal while the United States is exceptional among high-income countries for adhering to traditional Christian beliefs.