Mounting from the left or near side of the animal has its roots back in war, when horses were ridden by soldiers armed with swords. In order to avoid any potential debilitating incidents before engaging the enemy, riders would mount from the side where the sword would not impede the process. As most people would use a sword with their right hand, the scabbard hung on the left, so the left foot went into the stirrup on mounting. Most traditinal English riding has its roots back in the cavalry so this procedure of "always mount from the left hand side" has become, if you like, misinterpreted. Horses should be trained so that they accept mounting from either side. This is something that the animal can easily understand and accept. It is also useful to maintain the riders flexibilty if he/she can mount from the left and the right side.
Here are more opinions and answers from other FAQ Farmers:
- Left foot goes in left stirrup, swing the right leg over.
- You get on the left side of a horse, but it depends on the type of horse you have. Sometimes if you get on the wrong side, it will either try to kick you or it will run away.