Almost daily we come across — and many of us even use — familiar expressions that, when you come to think about them, really defy explanation.

As a person who’s made a living by using words, I confess I’m one of the biggest offenders; that is, I often use expression that I feel comfortable with and that I’ve heard before, but seldom am able to explain why I used such terms.

The one that I’ve struggled with is “having an ax to grind.” Surely you’re heard it, possibly even used it. When I first heard it, it was in the context of a faculty meeting at Highlands University, where I used to work.

The professorial crowd, working on proposed changes to the class offerings couldn’t agree on much. So protective were the instructors of their turf that they tried to vote down any proposal that didn’t benefit them directly.

We witnessed a lot of stalemates during those Wednesday afternoon faculty meetings. As we left, one of us said, “They just have an ax to grind.” To several in the group, that expression connoted the idea of sharpening an ax for use against fellow faculty members with whom they disagreed.

But far be it from college professors to even hint at violence, as our job was to think and speak only of lofty matters. The “ax to grind” expression puzzled me for a long time, until I came across a book, “Why You Say It,” by Webb Garrison, that list hosts of familiar but puzzling expressions.

So does the term really mean that we’ll make people’s heads roll? Not at all. It’s closer to having a hidden motive. Garrison’s explanation is about a person who owns a dull ax and stops by to admire a merchant’s new grindstone.

“Let me show you how it works,” the merchant says and proceeds to hone a sharp edge. The visitor, assuming the service is free, thanks the grinder and walks off.

An object that used to put the fear into us in the Immaculate Conception School classroom of Sister Mary Muchos Golpos was threatening to provide a custom-fitted dunce’s cap for the really difficult students.

What about having to wear the dunce’s cap? I’ve never seen one, except in comic books and movies. According to authorities, the cap-wearing student selected for the honor was usually slow and/or rebellious. According to Garrison, “Generations of Americans followed or tolerated that practice,” but few realized the term represented a noted scholar.

A Scottish-born John Duns Scotus founded a school in the 16th century in which the practice of donning the cap was frequently practiced. Most of us students at I.C. doubted whether the school even had such a hat, but the mere threat of having to hear one kept us in line. Usually.

As students at Highlands, many of my classmates employed the term “Freudian Slip” to remind one another to watch their tongue. The expression obviously comes from the founder of psychoanalysis, Sigmund Freud. One of Freud’s theories stated that every abnormal mental state involves repressed memories of the kind that evoke an “aha” reaction.

Often one who commits a Freudian Slip lets out a word or expression that’s sexual, causing that person to apologize, to assure all classmates that the slip was unintentional.

A lynching is the result of mob violence that has gone too far. A Captain William Lynch appears to have had the process named after him. In the state of Virginia, Lynch supposedly conducted a kangaroo court, heard brief testimony and then sentenced several ruffians to hang. The term Lynching Party stems from the captain who meted out justice in those days.

Have you ever experienced pandemonium? The term refers to Satan and his peers, and describes chaotic uproar. The word, coined by John Milton in “Paradise Lost,” has endured for several hundred years.

Did you ever consider looking a gift horse in the mouth? Garrison explains that if the horse is indeed a gift, the recipient ought not question the donor any more. Apparently, people with lots of horse sense can estimate the age of a horse by looking into its mouth. Additionally, to “get it from the horse’s mouth” means that you have received the unvarnished truth.

Have you ever met a person — usually a woman — who IS a spring chicken? The term, according to Garrison, has to do with the keeping of chickens, a practice that began in the dawn of civilization.

In those days, there were no incubators to keep chickens warm, no hen houses in which the fowls could luxuriate. The result was that chickens were best raised during in the spring for sale in the summer.

Even though many chicken sellers tried to pass off an older breed as spring chickens, buyers were suspicious and generally rejected the sellers’ claims.

What’s the difference between rhubarb and a Donnybrook? For one thing, a rhubarb takes place on the baseball field, usually as a result of a pitch that comes too close to the batter, or the act of digging one’s baseball cleats into the shortstop’s thigh when trying to advance a base.

Both terms deal with noisy fracases, but a Donnybrook gets its name from a place in Ireland, called County Donnybrook, where revelers were known to drink and celebrate boisterously, throwing fists and usually ending up in jail.

One theory as to the genesis of “rhubarb” explains that movie directors would hire extras for crowd scenes and instructs them to holler “Rhubarb, Rhubarb,” “to create the impression of angry chaos.”

Now, in addition to possessing a list of words we already use, we have some inkling as to their meanings.

Meanwhile, you can be assured that these words and their definitions are The Real McCoy.