Horse's Mouth

[essj]

What does the phrase 'Straight from the horse's mouth' mean and where did it originate.

[Quizmonster]

It originated in the fact that one can tell a horse's age by studying the state of its teeth. An unscrupulous horse-seller might try to con you but - if you know your stuff - you will not be deceived. Thus, information that comes 'straight from the horse's mouth' is indisputable.

We also have 'Don't look a gift horse in the mouth' on the same basis. In other words, it would be rude to look into the mouth of a horse you'd been gifted, as if you were checking out its age/value.

[Quizmonster]

I should have added above that there are some people who believe it comes from the world of horse-racing, whereby information 'straight from the horse's mouth' is the information to believe...ie where to put your bet on a race! The winning horse already knows, as it were!