INTERESTING NOTE:

In the American wild west, a careful horse buyer would go "straight to the horse's mouth." He would look at the horse's teeth - the longer the tooth, the older the horse, the lower the value of the horse.

Nowadays, people of advanced years or experience age are sometimes irreverently referred to as "long of tooth."

But there is also an interesting European origin for "straight from the horse's mouth." During the Napoleonic wars, the British employed prostitutes as spies. Their mission was to seduce French officers and give British intelligence the information they were able to obtain. When intelligence officers reported to their operational superiors, they were frequently asked if the information was authentic. The usual response was

"I got it straight from the whore's mouth."

Somehow, the pronunciation got changed through the generations and "whore" mutated into "horse."