Close but no cigar, fly off the handle, he is pulling your leg, I was beside myself—we see idioms like these all the time, even though the closer we look, the less sense many of them make.

Sometimes two familiar expressions get jumbled. When that happens, the result is what you might call a “Frankenstein formation,” a nod to the mad scientist who created a monster by conjoining parts that didn’t belong together.

One Frankenstein formation that may never go away is center around. You see and hear it everywhere. Two of the numerous examples found online: “The conflict centers around the atrocities of war.” “My research centers around the geometry of moduli spaces.”

The language scholar Wilson Follett calls center around a “geometrically senseless expression.” It results from mashing together center on and revolve around. Because those phrases are roughly synonymous, over time they merge in the mind.

Some otherwise intelligent language mavens now defend center around, apparently reasoning that if enough heedless people keep saying something, it becomes acceptable. Others are having none of it. As Paul Brians says in Common Errors in English Usage: “Two perfectly good expressions—‘center on’ and ‘revolve around’—get conflated in this nonsensical neologism. When a speaker says his address will ‘center around the topic of’ whatever, my interest level plummets.”

Another hardy Frankenstein formation is fall between the cracks: “News reports flash a daily barrage of stories about children who fall between the cracks.” “Every day this country’s health insurance situation lets people fall between the cracks.”

Picture a typical sidewalk. There are cracks—narrow grooves—at either end of the concrete slabs. So what is “between the cracks”? Concrete. Anything that falls between the cracks is falling onto a rock-hard surface.

Not only is that painful, it is not the intended meaning. The original expression is fall through the cracks, which connotes a different kind of painful experience: the pain of being overlooked, ignored, or abandoned.

One theory is that fall between the cracks resulted from scrambling fall through the cracks and fall between two stools, an idiom roughly meaning “to fail,” which dates back to the late fourteenth century.

Although some idioms are revealed as absurd under close analysis, many of them made more sense before time or misuse undermined them. Even if they now strike us as a bit off, like a daft but well-meaning old friend, it is up to us to ensure that nobody addles them further.