Will that be mineral, Evian or plain?

Jeffrey Whitmore on language traps:
"They laughed when I sat down at the table and ordered a glass of laxative.
I think that's why they laughed.
Maybe they were just amused at the sight of an old gringo fumbling with his school books, dictionary, street map, reading glasses, and the Spanish language.
I wanted a glass of purified water, but I couldn't remember the term agua purificada.
I gave it my best shot, and came up with agua pura.
Because my New England accent makes "water" sound like "watuh," I tried to emphasize the Spanish "r" in pura. I tried too hard and -- as I was told later -- my pura sounded like purga, meaning laxative.
Fortunately, they gave me what I wanted, not what I ordered."