Why Do We Say "Straight From the Horse's Mouth"?

The phrase "straight from the horse's mouth" suggests getting information directly from the most reliable source, but its origins are shrouded in mystery. Some theories suggest it's linked to horse racing, where bets are placed and the most trustworthy source is the one closest to the action. Understanding this saying helps us appreciate the nuances of language and how idioms evolve over time, often from surprising places like gambling culture. It’s a reminder of how deeply connected language and everyday activities can be.