A Mug of Coffee That is Called A Mug of Coffee

Do you ever feel like winding up the staff in Costa Coffee by going in and asking for a Venti?  (or asking for a Medio in Starbucks?)
On the one hand, it does make the coffee sound posher by giving the sizes fancy names.  And that's important - if you're going to spend the best part of four quid on a coffee (when you can buy a big jar of the good stuff for six pounds, I'm talking about Douwe Egberts, yeah baby) you need to feel as though it's something special.  That's why they go on about how drinking coffee in a shop, forced to share a table with strangers, is more sustainable than drinking it at home while sitting on furniture you like.
In your pajamas. (sorry, I should keep up with the lingo - "onesie")
But there is a lot to be said for having words that I know what they mean.  Tall, Grande, Venti - to me, of these three words, the two that sound bigger are "Tall", and "Grande".  I have no idea what Venti means.  Apparently it means twenty, to reflect the fact that a Venti drink is twenty fluid ounces.
I have a confession to make.
I have no idea how big a fluid ounce is.
Ounces to me mean weight.  There's sixteen ounces to a pound, two point two pounds to a kilogramme, and lots of kilos in a tonne.  I don't get the fluid ounce thing, and I'm sure it's really simple.
I would guess a fluid ounce is roughly a sup.  Not a sip - a sup, as in a sup of beer (NOT "suff", as some people say. Sup.).  Somewhere between a sip and a swig, enough so that you know you've drunk something, but not so much that you're halted from talking for more than a moment.
So twenty sups of beer doesn't sound a lot.  So Venti now doesn't sound big.
Except it is.  It's massive.
And while I'm on the subject, let's look at the term "Regular".  Regular, many many food outlets have decided, means small.
No it doesn't.  Regular means average.  And Average means medium.
Small, medium and large, that's all you need.  Or if you want a really big drink, massive.
Now I'm off for a Quinquinty Visto.
Or is that a computer program?
Ciao!
PS I have to say that the Chocolate Tiffin Triangles at Costa are bloody amazing though.  I'd have a Venti one of them any day.