"Trench Mouth" is a disease also known as Acute Necrotising Ulcerative Gingivitis (ANUG). I didn't think it was possible for a name like "trench mouth" to be less disturbing than its full medical name, but I can't think of anyone who'd put up with just two of those terms, let alone the whole quinella.
Since ANUG does such a great job of terrifying children into brushing, I think it's safe to use the term "Trench Mouth" for something else. I humbly propose: the act of accidentally saying something that would get you mistaken for a pedophile.
Naturally, I have an example.
I'm currently preparing to move into a new condo, and this requires something I never cared about before: curtains. After all, I lived in Grande Prairie for a year. It was practically a faux pas not to hang a Newfoundland flag in your apartment window. But that won't stand here, and so I found myself with an interior decorator, looking over fabric samples. (As a side note: she mentioned about four times which particular fabrics were light-blocking, which was ideal for shift work. Maybe we're not that different from Grande Prairie after all... or maybe I should have shaved that morning.)
On the drive home, I envisioned myself speaking to an eight-year-old Denton in 1984. How on Earth would I ever be able to face him, and admit that I spent an afternoon picking out drapes? He'd never forgive me. But maybe I could win back his trust by explaining the den. It's off to the side, without any windows, which makes it perfect for movies and video games. And I'm thinking about using it as a stage for film projects, too, so there'd be a dropcloth that hangs over one wall, and there'd be a camera on a tripod, and we could make movies. Doesn't that sound like fun?
And then the eight-year-old Denton in my head looked at me in silence for a moment, and then asked, "Doesn't that sound a lot like that special episode of "Diff'rent Strokes"?"
Normally, this is where a long, awkward silence would begin. But thanks to the power of language, only a short awkward silence is necessary! Then, I simply shrug and say, "Sorry. Trench mouth."
Remember those three words, my friends. They may save your job one day.