Beat around the bush: meaning to avoid or evade a particular topic, should be seen as an expression describing an act lacking the direct approach. It originates in the beaters who flushed out the birds in order to flush them out of their roosts and/or nests. The phrase first appears in the 1570s.
Under the weather: meaning to feel ill, originated at sea when sailors feeling unwell would go below decks to escape the elements – quite literally putting themselves under the weather. The phrase began to come into general use from around 1800.
A piece of cake: meaning ‘easily accomplished’ first appears around 1870. It is thought to have been derived from the awarding of cake in cakewalks (dances) in the US. In the UK, it is generally held to have been introduced from 1936 as RAF slang.
Break a leg: is to wish someone good luck, particularly in the theatre where wishing someone good luck is held to be bad luck. In the early days of the theatre the members of the troupe not performing had to remain behind the leg line – not until they crossed the line, thus breaking the leg, would they get paid. The phrase has been in use for a very long time and it is possible the idea first came about with the Ancient Greeks.
Costs an arm and a leg: or ‘expensive’, is not seen until the middle of the 20th century (although there are various unsubstantiated ideas the phrase dates from the 19th or 18th centuries). It is said to have begun as a comment about the high cost of medical care where limbs may still be amputated.
Once in a blue moon: describing a rarity, an actual ‘blue moon’ is the second full moon in a calendar month (the lunar month of 28 days being shorted than nearly all calendar months). Any blueness has nothing to do with the timing, the phenomenon is purely down to the observer. First seen in the middle of the 19th century, to have two full moons in a calendar month is not exactly that rare, indeed it has to happen on average every 33 months.
A blessing in disguise: or something which may prove rather better or more beneficial than is first apparent. It is first seen in 1746 in a work by James Hervey.
By the skin of your teeth: either barely avoiding or narrowly succeeding; it comes from the King James Version of the Bible, in Job 19:20, which reads: “My bone cleaveth to my skin and to my flesh, and I am escaped with the skin of my teeth.”
Barking up the wrong tree: pursuing a mistaken course of action, is first seen in the USA in the early 19th century. It began in reference to hunting dogs when pursuing such as raccoons, which may have left a trail to suggest they were up the tree but had escaped.
