Straight From The Horse's Mouth

              The idiomatic expression “ straight from the horse’s mouth ” means that the information is  true  and reliable because it comes from the original or authentic source.  Now , where did this expression come from ? Well , here’s the story . In the olden days , it was believed that the age and general state of health of a horse can be seen in its mouth and teeth . Thus ,  horse dealers   who wanted to avoid being  cheated by lying middle men would themselves go straight to the horse and  inspect its    mouth  and teeth . The expression  caught on and developed another shade of meaning . These days , it has a  figurative meaning that something is true or  correct .

Example : 

You better believe that the company will lay off  Mr. Jones soon . The Human Resources Director himself told me . So , it's really straight from the horse's mouth.