A "dark horse" is a term used to describe a little-known person or thing who emerges to prominence. From a novel, The Young Duke by Benjamin Disraeli.

A kangaroo court or kangaroo trial, sometimes likened to a drumhead court-martial, refers to a sham legal proceeding or court.

Namby Pamby is a term for affected, weak, and maudlin speech/verse. However, its origins are in Namby Pamby (1725), by Henry Carey.

No nothing to do with dice at all.
Dicey is somthing risky or dubious. Said to come from a crooked map seller who used worn out map plates to produce maps that he sold as original antiques. His name was Mr Dicey.

A white elephant is a valuable possession which its owner cannot dispose of and whose cost (particularly cost of upkeep) exceeds its usefulness.

17th century England the bigger the wig the higher the social status.

Originally a northern miners term which evolved from working miners being identifiable by their black boots and coal covered black trousers.

'Bobs Your Uncle'
Meaning that somthing will be resolved in your favour without much effort.
Comes from the 1890's when Arthur Balfour was suprise choice for Secretary of State for Ireland. It transpired that the Prime Minister Robert (Bob) Gascoyne-Cecil, Third Marquis of Salisbury was his uncle!

Kibosh: Stops you in your tracks, effectively the end of.

Early English medical theory suggested rubbing the hair of a particular dog into the wound of its bite would cure the ill effects and heal the wound.

After Thomas Hobson (1544-1631) of Cambridge, England, who rented horses and gave his customers the choice of the horse nearest the stable door or no horse at all.
Aged -MA on 2nd skill.

Dates to the middle ageswhen it is said the only part of a pig that could not be eaten or used in any way was the ear.

Warts & All means to include every detail however unsavoury.
This comes from a painting of Oliver Cromwell of which he said he would not pay for unless it showed all his 'roughness, pimples, warts and everything as you see me'.

To make a challenge. From the days of prize-fighters at local fairs. When it is your turn to fight your hat is shown to the crowd and you step forward.