A juggernaut is huge truck or lorry and in an extended sense a force without mercy that crushes everything in its path.
As a word juggernaut comes directly from Hindu mythology and the Hindi language. It originally referred to a large wagon that carried the image of a Hindu god at annual processions of chariots as part of a religious festival. These festivals continue today with the chariots or floats often being 12 meters high. But for over 500 years ( the term was first used in English in 1321), the main thing English-speaking observers noted about these festivals were that devotees threw themselves under the wheels in a sort of religious sacrifice. And so the connotation of a crushing force was added to the Juggernauts.
Marvel comics saw the potential for a captivating superhero first, and the Juggernaut made its X-Men debut in 1965.
