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Common Idioms and Phrases > D-Letter Sayings
Note: The definitions for sayings can be found with ease, but finding the origins of phrases can prove far more challenging. Looking back through history, it's tough to find the place or person in which a phrase has its roots. We are limited to what can be found in writings, such as books, poems, newspapers, and plays. Often times, phrases will be quoted from century old newspapers, or from plays that were done in the 17th century by playwrights like William Shakespeare.

The phrases that are quoted from these books, poems, etc., are likely already widely known, and have their origins some place older. For instance, just because an idiom shows up in a newspaper from 1850, does not mean the idiom originated from that newspaper. However, what that does tell you, is that the phrase was being used since 1850, so its origins are at least more than 150 years old. - Meanings and Origins of Phrases
A tense situation where the outcome is clear only in the last few seconds.
This phrase is commonly used to describe dramatic moments where the final result
is not known until the very end, or near the end. For instance, a sports commentator
for a basketball game might describe a close match between two teams as "coming
down to the wire." This is often said towards the end of a close game because, due
to the game being so close in terms of score, it's difficult to tell who will win until the
final moments.

So where did this phrase come from? This expression is believed to have originated from horse racing, where a wire was hung up over the finish line to help determine a winner. Thus, races that were extremely close could be described as "coming down to the wire," quite literally.

According to World Wide Words, the phrase is used by Scribner's Magazine in July, 1889. There's a story within the magazine titled 'How the Derby Was Won', and it provides some details about a horse race:

"As the end of the stand was reached Timarch worked up to Petrel, and the two raced down to the wire,
cheered on by the applause of the spectators. They ended the first half mile of the race head and head,
passing lapped together under the wire, and beginning in earnest the mile which was yet to be traversed."

Reference: had Scribner's magazine where, which is where the above quote is from.
* With the game clock running down and both teams being tied in score, this is an exciting game that is going to  come down to the wire!

* It was a battle of strength that came to the wire when I challenged my friend to an endurance test to see who could finish the most amount of push-ups in the least time.
The meaning of the phrase Down to the Wire.
Origins for the idiom Down to Wire.
Phrases and Idioms