History The term "megacity" entered common use in the late 19th or early 20th centuries; one of the earliest documented uses of the term was by the University of Texas in 1904.[12] Initially the United Nations used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million.[13] In the mid 1970s the term was coined by urbanist Janice Perlman referring to