This week the government announced that it would subject persons convicted of terrorism offences to lie-detector tests before early release. Such tests are known as “polygraphs”, which definitely sounds more scientific. But is it?

“Polygraph” comes from the Greek for “much writing”, and in the late 18th and early 19th centuries it denoted someone who wrote vast quantities, as well as a mechanical contraption that enabled the user to write two copies of a letter at once, and so metaphorically a person who resembled someone else in every detail.

It was the late 19th century when a “polygraph” came to mean a device capable of recording (and “writing”) multiple physical measurements simultaneously. In the 1920s, a young American physiologist named John Larson devised a version for detecting liars, which measured blood pressure, respiration, pulse rate and skin conductivity. Larson called his invention, which he took with him to the police, a “cardiopneumo psychogram”, but “polygraph” later became the standard term. To this day, there is no reliable evidence that polygraphs actually work, but the great British public will no doubt be reassured by official PR that makes our masters sound like the heroes of an FBI crime series.

• Steven Poole’s A Word for Every Day of the Year is published by Quercus