Also due tomorrow: a set of plastic drinking tumblers; four each of four colors for 25 bucks. That's gonna make my life a lot easier. I'll use 'em every day, and they'll last for years and years. I don't mind splurging on Crystal Geyser now and then (and I'm certainly not going to feel guilty over it) but Portland tap water is perfectly fine and it's (effectively) free. I'll be able to use these tumblers daily without anxiety over dropping and breaking them; the set is big enough that I'll be able to use them with guests, and the different colors will help to keep them from getting mixed up.
And why is it called a 'tumbler', anyway? After a quick internet search (and filtering out references to a certain popular social-networking site) I learned from Wiki that
They are so called because such glasses originally had a pointed or convex base and could not be set down without spilling. This compelled the drinker to finish his measure.
So there you have it. It's one of those names that stuck, like 'trailer', even after the thing had lost the salient feature for which it was named.
I learned incidentally that there is a classic Russian design known as 'granyonyi stakan' (called a table-glass in English) that's distinguished by the polygonal, faceted shape. Looking at the illustration, I believe the plastic tumblers we used in our family when I was growing up may have been a copy of this design.