Short answers, pulled from the story.
François Magendie labeled phrenology a pseudo-science in 1843. This early label marked the beginning of a long philosophical struggle to separate genuine science from claims that mimic it without following its rules.
The word pseudoscience derives from Greek roots meaning false knowledge combined with Latin words for understanding. It entered common usage by the late 18th century when James Pettit Andrews wrote about alchemy in 1796.
Karl Popper argued that astrology fits this category because no observation could ever disprove it. He believed that if a theory cannot be falsified, it often falls into pseudoscience regardless of how many people believe it.
Anti-vaccine activism has persuaded large numbers of parents to skip vaccinations citing research linking childhood vaccines to autism. Andrew Wakefield published a study claiming gastrointestinal disease occurred within two weeks of receiving shots before the publisher retracted the paper and he lost his medical license.
The Communist Party of the Soviet Union declared Mendelian genetics pseudoscientific during the mid-20th century. They sent prominent scientists like Nikolai Vavilov to Gulag camps for opposing this view.