I don't think anyone did. Humans just have a craving to do things that make them feel unique or extraordinary. Having any skill or ability that defies current scientific knowledge or human understanding makes a person "superhuman"
The definition of superhuman put into layman’s terms is a human exceeding normal everyday human activities. A superhuman is a person with extraordinary abilities for example, surviving a lightning strike, being able to endure freezing temperatures, or lifting a car.
To mean I think it means being powerful ND capable of doing certain things which other human beings cannot do. For example ability to fly, being genius among others.
The phrase "Super-human" is defined in the Super-Human classification of the Humanoid Classification Plan. The definition is "a human being who is above the human level of intelligence" . So, a super-human is someone who is much smarter than a human. They are not limited to humans, but are defined as people who are "above the human level of intelligence."
superhuman beings. : exceeding normal human power, size, or capability : herculean. a superhuman effort. superhuman strength. also : having such power, size, or capability.