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Some words used to have a different meaning. For example, according to this link, here are a list of twenty words that originally had a different meaning from the connotation that we associate it with today. One example would be nice. Before nice meant silly, now nice means that a person is kind or the antonym of mean. Is there a single-word or phrase that describes the phenomenon. It kind of reminds of a paradigm shift in science, when an idea that was thought to be true is changed. For example, the heliocentric theory replaced the geocentric theory.