Q: In describing a tech device, “the size of a pack of cigarettes” seems to be a dying locution. Of lung cancer, presumably. I prefer “the size of a PDA” (i.e., like a palm handheld).

A: You can never tell which expressions of comparison are going to become dead locutions and which aren’t. Just look at “bigger than a breadbox.” The phrase was invented by Steve Allen when he was a regular on the old “What’s My Line” television show; panelists had to ask yes-or-no questions and Allen came up with “Is it bigger than a breadbox?” Real breadboxes aren’t seen much anymore, but you can still hear that old expression.

As for “the size of a cigarette pack,” no one is likely to forget where that one came from any time soon (unfortunately!).

Many phrases live on even after most people have forgotten where they came from. “Bellwether” is a good example; it refers to the lead sheep in a flock (the castrated ram, or “wether,” that wears the bell). “Linchpin” is another: a pin inserted into the end of a shaft or axle to keep a wheel from falling off. The meaning was once “real” but now it’s purely metaphorical.

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