In 1599 English writer and traveller Richard Hansard wrote: "It hath been an antient custom among them [Hungarians] that none should wear a fether but he who had killed a Turk, to whom onlie yt was lawful to shew the number of his slaine enemys by the number of fethers in his cappe." It was a symbol of honor and achievement then and remains so today. But most people today would consider sticking a feather in your cap, literally or figuratively, is a bit pretentious. ( source )

The original origin of this phrase is unsettling and disturbing at best. It was used, originally, in reference to a woman who had been dishonoured through rape and/or loss of virginity. Nowadays it is used to refer to something like a skit not being well done. As in, "watching that play was a fate worse than death."

This phrase doesn't have an origin in which it meant something and became what we know it to be today. Apparently the phrase has existed for at least 200 years and was used quite a bit in the 1800s. It's meaning is to stay strong in the face of adversity. ( source )

George Bernard Shaw seems to have been the first to use this phrase in a figurative sense. And it seems that the figurative meaning is the same as the literal. Taking a shot in the dark is a hopeful attempt at success. ( source )

This phrase was used a lot in 1953 but an earlier citation puts it at 1940 in a Metals and Plastics Publications advertisement. Read about it here . The phrase means you get more for your money.

Originating in the sport of boxing this phrase has to do with the countdown a ref gives when one of the boxers hits the floor and can't get back up. In a figurative sense it refers to someone being unable to complete something and is defeated. 

One for the road has to do with beer, or alcohol, and the consumption of it before leaving the establishment (i.e. pub or bar) or for a journey. In 1939 it was used in a report about the dangers of drinking and driving. Read all about it here . 

There are some really interesting theories about the origin of this phrase and what it could mean. But the real story has to do with just sleeping. Read about the theories and the reality here . It's used to wish someone a good and sound night's sleep.

Jim Hawthorne, a West Coast radio disk jockey, with popularized the idiom in the late 1940s. Citing a May 10, 1948 Time magazine article, Hawthorne is quoted as saying his broadcasts were carried over five Southern California stations on what he called “the net-to-net coastwork of the Oh-So-Peachy-Keen Broadcasting Company.” He also was the author of that popular phrase, "I mean, can you dig it, daddy-o? Neat-o!"  The idiom's origin is unknown but it was always used to signify that something, someone, some situation, or event were superlative in the coolest, funniest way. But with continued use it has eventually become a phrase that carries with it a hint of sarcasm, irony, or condescension. ( source )

This is a newer idiom, born in the 1990's. And it truly means the other person can talk to the hand because the person isn't actually going to listen or is listening. Read about the origin here . 

When this phrase first came into saying the word 'fit' didn't mean what we think of today - fit as in fitness. It meant 'suitable' or 'seemly'. Read about the phrase here . We say it today to mean someone is fit - as in fitness. *wink*

While Shakespeare penned this phrase in 1595 he isn't credited with the phrase becoming a known one, firefighting is. As a way to ensure large fires wouldn't cause damage firefighters would set, on purpose, smaller control fires to mitigate danger. So they actually fought fire with fire.  Today we use it in a figurative sense to indicate someone responding to an attack by using a similar method as one's attacker.

The origin of today's idiom is quite literal. Apparently in the game of marbles you hold them with your knuckles down. So in the game knuckles down means you are playing a serious game. When we say it today we are saying, "Get down to business." ( source )

Goody Two-Shoes is a poor orphan named Margery Meanwell who only has one shoe. When she's given two shoes she is so happy she tells everyone she meets. Her story is found in the 1765 nursery tale The History of Little Goody Two-Shoes. Read here about how goody got added to her name.  These days the phrase means that the person being called a "goody two shoes" is smug and above virtuous. 

The envelope that this phrase originated around was not an envelope that we use in written correspondence. It was the mathematical envelope. I read the word 'mathematical' and my brain shut down so you'll have to read about this mathematical envelope here . *grin* When we say it today, however, we aren't referring to anything math related (thank goodness for me). What we are saying is that someone is pushing the limits or boundaries of what can be or should be done.

Sometimes the theory of the origin of a phrase is more interesting that the actual origin. I personally think that is true in the case of today's idiom. 'On the ball' is the short version of the common phrase 'keep your eye on the ball'. One of the ideas about this phrase has to do with a time-ball at the Royal Observatory in Greenwich. Read about it here and about the actual origin of the phrase. We use the idiom today in much the same way it was meant when it came into being - be alert.