So its a paper cup... why do americans make up such weird names for stuff, why cant you just call it a paper cup..? ROTFL!
It's a tradition, especially pronounced in the 19th century: either calling something by the name of the inventor or producer, or just finding a round-about name to call something, i.e. "cackleberries" for eggs. We have Bowie knives, Ball jars, Kleenex, Scotch tape, cardigans, and anything high end used to be "Cadillac". This still persists quite strongly in trades, maybe just to confuse the apprentices. Why? Because it's an Americanism; part of the national character.
A lot of products' names are
brand names. That is, they take their names from the product brand. Kleenex tissues come from Kleenex, a brand by Kimberly-Clark company. Dixie company makes paper cups and calls them "Dixie Cups". To
Xerox something is to photocopy it, first accomplished with a machine from Xerox Corporation. Another company may introduce their brand of tissues on the market, but they may still be referred to as "Kleenex tissues" because of the first association with that name. A follow-on company's paper cups (or small plastic cups) may be referred to as "Dixie Cups".
Quite often, the company that introduces a product on the market
first is the most visible, memorable, and longest-lasting product because the name is seared into customers' minds.
-Boofer-