Guide to idioms: Lets the cat out of the bag

Have you ever wondered why we pass the buck, eat humble pie or let the cat out of the bag? The English language is rich in idioms and expressions that have evolved in meaning over the centuries, often arising from trades or customs that have long disappeared.

The origins of hundreds of everyday words and phrases have been set out in a new guide called The Etymologicon. Its compiler, Mark Forsyth, has traced them through books and writings, some dating back to Ancient Greece. Mr Forsyth, a writer and etymologist, said: “What I love about etymology is the strange back alleys and extraordinary and ridiculous journeys that words take."

Much of his research was carried out in the British Library, following references through a succession of dictionaries back, as far as possible, to their original sources. There are competing theories about the origins of some phrases, but he has selected those that are supported by the most evidence. Sir Winston Churchill emerges as a prolific source of words, credited with inventing, among others, the terms out-tray, social security and seaplane.

The book also describes how “hello” was popularised by the advent of the telephone. Until then, it had been an obscure greeting, with good morning, good day and good night being used. Alexander Bell, credited with inventing the telephone, had favoured the nautical “ahoy” as a short, standard salutation, but it did not catch on.

Other words and phrases to feature in the guide include:

Cold shoulder — Cold shoulder of mutton was the sort of leftovers given to unwelcome house guests.

Bite the dust — A direct translation of a quote from The Iliad in which a character talks of the death of Hector.

Humble pie — A meal made using the “umbles” — innards — of deer and only eaten by the lowliest servants.

Film buff — From buffalo, the leather worn by 19th century New York firemen who drew crowds when tackling fires. These aficionados became known as buffs.

Nazi — An insult in use long before the rise of Adolf Hitler's party. It was a derogatory term for a peasant, being a shortened version of Ignatius, a common name in Bavaria, from which the Nazis emerged. Opponents then shortened Nationalsozialistische Deutsche Arbeiterpartei.

Let the cat out of the bag — In medieval markets, piglets were sold in bags. A common con was to switch the valuable animal for a worthless cat or dog: buyers were either sold a pup, or, if they discovered the ruse, let the cat out of the bag.

Average — From an old French term avarie, meaning “damage done to a ship". Vessels were often co-owned and when repairs were carried out, owners were expected to pay an equal share, the average.

Bizarre — From the Basque word for beard, bizar, because when bearded Spanish soldiers arrived in remote Pyrenean villages, locals thought them odd.

Bigot — Old English for “by god", to describe someone who asserts their own saintliness, while being a hypocrite.

Soon — The Anglo-Saxon word for “now” — more immediate than its current use.