You scratch my back; I’ll scratch yours.

This is one of several shortcut definitions for “quid pro quo,” the term that we have been hearing for the past few weeks ad nauseam.

President Trump has denied any quid pro quo in his dealings with the Ukrainian president by threatening to withhold aid from the country unless an investigation of the Bidens was undertaken, but acting White House Chief of Staff Mick Mulvaney muddied the waters by undercutting that denial then trying to walk it back.

Despite having had two years of Latin under Edgar Miller at Summit Hill High School way back when, I can’t ever recall having used the term “quid pro quo,” even though I have heard it used occasionally in courtroom cases that I covered as a reporter.

If you do not speak Latin (who does these days) or might be unacquainted with legal jargon, the general idea behind quid pro quo is “something for something.”

Even though we have rarely if ever used the term doesn’t mean that its application has been absent from our lives.

For example, when I asked a friend to pick me up from the airport a few weeks ago, I suspected he had filed away his doing me this favor in case he needed me to come up with a quid pro quo. A few days later it did when he asked me to drop off his daughter and her friends at a high school football game.

The term dates to the 16th century and has its origins in medicine. The phrase meant that one medication had been substituted for another, something on the order of a generic today being substituted for a more costly brand name.

Back then, however, it was more common for fraudulent substitutions to be made which could be dangerous, even fatal to a patient.

A century later, the expression came to be known as something done for personal gain or with the expectation of getting something in return, a closer meaning to today’s usage.

In common law, quid pro quo came to indicate that an item or service had been traded in return for something else of value. A contract, therefore, involved the quid pro quo of exchanging something of value for something else of value.

Bartering, for example, involves a quid pro quo when used in this context. You give me something, and I will give you something of close to equal value, but no money changes hands.

The same is true when a person buys property for cash — ideally, the money on one hand equals the value of the property on the other.

As time went on, however, the term quid pro quo took on negative connotations, which we now see in the allegations of the Trump-Ukrainian issue. When a person of authority either implicitly or explicitly uses that authority as a weapon to encourage an unsavory or illegal activity in exchange for something of value, this is a darker, possibly even illegal, example of a quid pro quo.

We are told to believe that those who make large donations to support political candidates are doing it because of their belief that this candidate is superior to his or her opponent.

Of course, in reality, we wonder whether there will be a quid pro quo if the supported candidate wins the election.

With the focus on the #MeToo movement, quid pro quo harassment has made a front-and-center appearance.

This is what Harvey Weinstein is alleged to have done.

Quid pro quo harassment occurs when a boss demands sexual favors or sexual contact from an employee or job candidate as a condition of employment.

In cases such as these, the boss uses his or her position of authority to try to force sexual favors in return for employment or continued employment.

Although we don’t use the term “quid pro quo” in everyday language, it still comes down to being synonymous for terms we do use, such as “one hand washes the other.”

By Bruce Frassinelli | tneditor@tnonline.com