DID YOU KNOW that the principle of leading horses, doing up their tack, and mounting from the near side (the horse’s left) goes back to the days of wearing swords on horseback?
Since a sword is usually hung from the left hip, mounting from the left means the scabbarded sword does not have to cross the horse’s back as the rider swings his leg over. Also, if you are mounting with sword in hand, your left hand is able to control the reins, and the right hand your sword, as you mount.