Quinsexagintillion comes from the extended system used to name extremely large numbers, where Latin-style prefixes are combined to build ever longer -illion words. Online, it has become a handy piece of shorthand for a quantity too large to picture, rather than a term most people use in everyday maths. Creators drop the spoken word into memes, reaction videos and jokes about wealth, scores and statistics, because simply saying it conveys scale better than any ordinary number. Its appeal is the sound itself: long, formal and faintly ridiculous.