Michelle Rafferty at OUPblog has a post on "Why the Trenta?" (1/24/2011), which includes this interesting Google Chat exchange with her friend Gabe, who "specializes in buying and selling unroasted green coffee from all over the world and loves discussing anything and everything related to coffee":
Me: So you work in coffee. What do you think of this whole Trenta thing?
Gabe: Honestly, this is about McDonald’s. They are very successful with their iced coffee and Sbucks is trying to compete. […] They have already lost a lot of customers to McDonalds/ McCafe due to quality and price. McDonalds has better coffee.
Me: Whoa, really?
Gabe: Yeah, McDs has won numerous blind tasting competitions and they have cheaper prices.
So I think that this is an appropriate time to bring back a comment by Stefano Taschini on an earlier LL post about names for coffee sizes ("Latte Lingo: Raising a pint at Starbucks", 11/30/2004):
I believe there must have been a small mistype: technically, a warm liquid that you ingest in quantities exceeding half a liter is "stock" not "coffee".
That was in reference to the "venti" (591 ml.) size, which is a bit more than an (British Imperial) pint (568 ml.). The trenta will be used only for iced coffee and other cold drinks, and at 916 ml. is almost but not quite a (U.S. Customary) quart (946 ml.).
Nor can I resist reprinting Dave Barry's opinions on names for coffee sizes borrowed from Romance languages:
We begin today with a disturbing escalation in the trend of coffee retailers giving stupid names to cup sizes. As you know, this trend began several years ago when Starbucks (motto: "There's one opening right now in your basement") decided to call its cup sizes "Tall" (meaning "not tall," or "small"), "Grande" (meaning "medium") and "Venti" (meaning, for all we know, "weasel snot"). Unfortunately, we consumers, like moron sheep, started actually USING these names. Why? If Starbucks decided to call its toilets "AquaSwooshies," would we go along with THAT? Yes! Baaa!
Recently, at the Dallas-Fort Worth International Airport and Death March, Mister Language Person noticed that a Starbuck's competitor, Seattle's Best Coffee (which also uses "Tall" for small and "Grande" for medium) is calling ITS large cup size — get ready — "Grande Supremo." Yes. And as Mister Language Person watched in horror, many customers — seemingly intelligent, briefcase-toting adults — actually used this term, as in, "I'll take a Grande Supremo."
Listen, people: You should never, ever have to utter the words "Grande Supremo" unless you are addressing a tribal warlord who is holding you captive and threatening to burn you at the stake. JUST SAY YOU WANT A LARGE COFFEE, PEOPLE. Because if we let the coffee people get away with this, they're not going to stop, and some day, just to get a lousy cup of coffee, you'll hear yourself saying, "I'll have a Mega Grandissimaximo Giganto de Humongo-Rama-Lama-Ding-Dong decaf." And then you will ask for the key to the AquaSwooshie. And when THAT happens, people, the terrorists will have won.
Note however that 7-Eleven has long since blazed a trail into the land of extraordinary drink sizes with the "Big Gulp" series, with a 32-oz. basic "Big Gulp", and other sizes as follows:
20 US fl oz (0.59 l) Gulp
44 US fl oz (1.3 l) or 1.2 l (41 US fl oz) (depending on region) Super Big Gulp
64 US fl oz (1.9 l) Double Gulp
128 US fl oz (3.8 l) Team Gulp
Note that except for "super" and "double", these are all Anglo-Saxon morphemes.
I haven't been able to find any recent information about McDonald's range of drink sizes, or their current size nomenclature — thus this page gives only one size per beverage type. But traditionally, they used small, medium, and large, with other names like "child" for something smaller than small, and "summer" for something larger than large.