If something comes “straight from the horse’s mouth,” that means it comes directly from its source—particularly if that source is in some way authoritative, reliable, or lacking any kind of distortion or manipulation. But how exactly have horses’ mouths come to be associated with such direct honesty and reliability? 

The History of “Straight From the Horse’s Mouth”

This phrase seems to have emerged sometime around the turn of the 19th and 20th centuries, apparently in the United Kingdom. Although the Oxford English Dictionary’s earliest attestation of the phrase appears in an article written by the novelist P. G. Wodehouse in 1928, its date of origin has since been pushed even further back to the late 1800s. 

“As the great British nation takes far more interest in horse racing than in politics,” read an article in London’s Reynolds Newspaper in 1896, “we’d get all our tips straight from the horse’s mouths, instead of being deluded and swindled every day by their lordly owners.” 

Unearthed by the etymologist Gary Martin, the wording of that early quote suggests that the phrase was already well established enough in language at the time to be used without explanation. 

As a result, we can presume readers would already be familiar with it, and so it must have been coined sometime earlier than even that date might suggest. But that quote also suggests that a popular theory claiming to explain this phrase’s origin might not actually be true. 

Straight From the Horse’s Teeth?

A commonly held theory about the origins of this phrase is that something that comes “straight from the horse’s mouth” alludes to the veterinary practice of assessing how old a horse is by examining its teeth. 

Looking into a horse’s mouth is one way to get an authoritative assessment of a horse’s age. Younger horses are considered of greater value than older horses to dealers and racing moguls, understandably, and so some unscrupulous dealers used to doctor or even cut down a horse’s teeth to pass it off as younger or healthier than it truly is—a practice once known as “bishoping.” 

The Most Likely Explanation For “Straight From the Horse’s Mouth”

The Reynolds Newspaper quote above, though, appears to suggest the original context of this phrase wasn’t a discussion about a horse’s age from the point of view of a prospective buyer or dealer, but instead a reference to a horse’s worthiness on the track, and the frequently unreliable betting “tips” that would influence a gambler’s choice of wagers. 

While those who were really in the know down by the trackside would sometimes be able to offer bettors decent advice, it seems this phrase alludes to the dream of receiving a tip from an even more authoritative source than that—namely, the horse itself. 

So, all told, the phrase “straight from the horse’s mouth” seemingly derives from the best possible—if rather imaginative—source of racetrack betting advice.

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