"very much, extreme," 1979, from Italian mondo "world," from "Mondo cane," 1961 film, literally "world for a dog" (English title "A Dog's Life"), depicting eccentric human behavior; the word was abstracted from the original title and taken as an intensifier.
Very large or very much; humongous, important: She had a lot of things on her desk top, including a mondo-size slo-mo printer/ I've got a mongo bruise on my leg from field hockey/ You'd think it took some kind of miracle, or some mondo engineering breakthrough
adverbVery; totally; fully, way: Your dad is mondo cool!/ mondo fun at the beach
[1979+; fr Italian mondo, ''world''; the mongo variant is probably just imitative]