Short answers, pulled from the story.
Record dealers in the United States began inventing names for obscure vinyl records in the early 1970s. They created retroactive categories like Northern soul and garage punk to increase the value of forgotten singles.
The term chillwave was coined by the music blog Hipster Runoff around 2009. It gained mainstream currency in early 2010 when it became the subject of articles by the Wall Street Journal and the New York Times.
Glenn McDonald developed genre mapping data in 2013 while working at the Echo Nest. He created the Every Noise at Once website and added the term hyperpop to the Spotify algorithm in 2018.
Netflix identified 76,897 different microgenres in its algorithms in 2020. The company used this data to develop successful series like House of Cards and Orange Is the New Black.
The term microgenre appeared in a 1975 French article to define a narrowly defined group of texts connected in time and space. It was originally used to describe historical fiction before the music industry adopted the concept.