Reviewed earlier here.
The origins of more idioms as promised:
Cold feet - in a book by Fritz Reuter (1862) a poker player who doesn't want to lose his fortune, excuses himself from the table because he has cold feet.
Curry favour - In a French poem, Fauvel is a dangerous centaur. Sycophants would curry (grooming) favour (Fauvel), to stay in his good books.
What the Dickens /Dickens to pay - Back in the 16th century the devil was Devilkin, usually pronounced 'Dickens'.
Good egg - In Captain Priest (1855), "In the language of his class, the Perfect Bird generally turns out a bad egg." That is an egg that appears perfect but is bad on the inside. The phrase was eventually reversed to describe decent people as 'good eggs'.
As sure as eggs is eggs - A misquote from logic: as sure as x is x. Used by Dickens, either on purpose or by accident.
Sour Grapes - In one of Aesop's Fables, a fox repeatedly tries to jump up to get a hold of some grapes. In the end the fox gives up and convinces himself that the grapes were sour and he didn't really want them.
Berk - slang, shortened from Berkshire Hunt (yes,quite)
Berserk - From Norse mythology, these warriors were wild and uncontrollable and would cast their weapons aside and fight empty handed.
Gone Doolally - 19th century, British Empire. In reference to the military base at Deolali, 100m north of Bombay. Because ships left from Deolali to Britain just twice a year, soldiers were often had to wait for long periods and the exhaustion and boredom could result in strange and eccentrc behaviour. The base also contained an asylum.
Wreak havoc - Began life as "Cry Havot", the frech call for plundering once a battle was won. Richard II banned use of the phrase on penalty of death but it was brought back to life by Shakespeare.
In cahoots - American term developed from the French 'cahute', meaning a small hut, somewhere people could collude unseen.
Use your loaf - slang, loaf of bread, head.
Plum Job - Plum was a slang term for a thousand pounds.
Not a sausage - slang, sausage and mash, cash
Take umbrage - Latin roots, 'umbra' means shade; to be put in the shade, feeling resentment.
Scot free - a 'scot' was a tax imposed on the Scandinavian people in the 13th century. Peasants were exempt, hence 'scot free'.
The Ancient Greeks and Romans
Bit between your teeth - i.e. unbridled enthusiasm. If the horse has the bit in his teeth as opposed to at the back of his mouth, he is insensitive to the rider's instruction and uncontrollable. In 470 BC, the Greek Aeschylus said "You take the bit in your teeth like new-harnessed colt".
Go with the flow - From Marcus Aurelius' Meditations, in which he said it was better to go with the flow" rather than to change the natural course of things, and "all things flow naturally".
Not worth his salt - workers were often partly paid in salt, known as salarium, from which the modern word 'salary' derives.
Scallywag - Latin 'scurra vagus' meaning wondering fool.
To set off on the wrong foot - Superstitious belief that left-sided things were evil and you should start your journey with the right foot first.
Lick something into shape - Belief that animals would lick their newborn into shape, esp. bears.
Take with a pinch of salt - Based on the story of King Mithridates of Pontus, who built immunity to poisons by taking a doses of poision with a single grain of salt to make them more palatable.
Spill the beans - Voters placed a white or brown bean into a jar and the outcome would be known if the jar was spilled.
Lost their bottle - a boxer's water bottleman may conveniently disappear when the boxer was taking a beating, forcing a premature end to the fight. Phrase started as 'lost his bottleman' to indicate cowardly behaviour.
Bandied about - from the game of Bander, involved hitting a ball to and fro.
Down to the wire - a wire would be placed above the finish line of a horse race with somebody watching over to determine who crossed the wire first.
At the drop of a hat - sporting referees would often drop hats to signal the start of a race, boxing match, etc.
Keep it up - phrase used in Victorian garden badminton
Nick of time - nicks were carved into a piece of wood to keep score. A last minute point was a 'nick in time'.
Throw your hat into the ring - the public threw their hats into a ring to challenge prize fighting boxers. The hats were collected in a pile and then shown to the crowd for the owner to step up.