The English language is full of strange idioms, many of them that we use without understanding how that phrase came to being. I only have time for a few but I might add more later. Let’s take a look at them shall we?
Train of thought: The process and direction of one’s thoughts
From the early 14th century, the word “train” meant a “drawing out or delay” of something. In the mid-15th century, the word evolved to include a “retinue or procession”. The first example of the term “train of thought” was attested in the 1650s whereas the first use of the word “train” in the sense of a locomotive. As a result, the idiom “train of thought” has nothing to do with trains (the transport) and is more likely to derive from a “delay” of a “procession” of “thought” (hence losing your train of thought).
Cup of Joe: Coffee
There are a few theories on this one. I’ll talk about the two most popular ones here.
The first is attributed to Secretary of the US Navy, Josephus Daniels (1862-1948), for banning all US Navy ships from serving alcoholic beverages. As a result, sailors resorted to the next strongest drink: coffee.
The second is a reference to a “cup of jamoke” as coffee is a compound of Java and Mocha. The term jamoke has been used in popular culture before, hence a “cup of joe” being derived from a “cup of jamoke”.
Beat About/Around the Bush: To avoid getting to the point
The earliest example of this term was recorded around 1440 in the poem Generydes – A Romance in Seven-line Stanzas.
Butt as it hath be sayde full long agoo,
Some bete the bussh and some the byrdes take.
This anonymous poem exists only as a single handwritten manuscript in the library of the Trinity College and Cambridge. The implication of this was that it was worse to “bete the bussh” than to “take the byrdes”. The next earliest example of the modern day phrasing of the term can be found in George Gascoigne’s Works, 1572.
He bet about the bush, whyles other caught the birds.
Technically, the correct phrase, if you stick to the origins of the word, would be “beat about the bush” but the incorrect US version took over in around 1980 so now most people say “beat around the bush”.
Gung Ho: Over-enthusiastic attitude towards doing something
This word was adapted from the Chinese military motto meaning “work together” (the word being kung ho). Lt. Col. Evans Carlson used this term frequently during World War II, where he would hold gung-ho meetings for his troops. They would discuss their problems and orders at these meetings. The expression became even more popular after the movie Gung Ho! in 1943 depicting a marine who did everything it took to get the job done.
Take the cake: Taking a prize symbolising victory or success
While it is widely believed that the phrase originated from the strutting competition known as the “cake-walk” in which the winner would have been said to have “taken the cake”, where cake was often the prize. This was popular within the black community of Southern USA in the 19th and early 20th centuries.
However, this expression has existed since the early 5th century BC where the Greeks used “take the cake” as a symbol for taking the prize. In 420 BC Aristophanes wrote “The Knights” (a criticism of the powerful Athenian politician Cleon).
If you surpass him in impudence the cake is ours.
The term “take the biscuit” is used the same way.
Early bird (takes the worm): Opportunity goes to those that are prepared
This is a tough one; the first recorded example can be found in John Ray’s A collection of English proverbs 1670, 1678.
The early bird catcheth the worm.
However, this suggests that the word was already in popular usage.
EDIT: I’ve added a part 2 with another three idioms.