My crazy little Pug dog knows what WHOA means. If we walk up to an intersection I say Whoa. It just comes out of me naturally, since that's been the stop word my whole life. Why shouldn't a dog stop for that word? He hears the sound and makes the association.
In Western riding, a horse is trained to jog (trot) from a cluck sound, and lope (canter) from a kiss sound. I had my horse trained backwards. My two Appaloosas are trained the right way around now, so that anybody can ride them and they're on with the program. Critters can be retrained too, but it really is best to get it right the first time.
This reminds me of the story of the Pastor's horse.
He was like me with my dog; his horse was trained with terms he was familiar with. To move on, his horse responded to "Praise the Lord," for a brisk trot, "Hallelujah" and to stop, of course, "Amen."
One day a fella was desperate for transportation to the next town, and asked the Pastor if he could borrow his horse for the day. The Pastor agreed but first had to explain how the horse was trained. The young man tried it, got the horse all figured out, thanked the Pastor and was on his way.
The horse plodded along reliably, until the young fella decided he'd like to get a move on. He couldn't remember the cue to go faster and no amount of kicking would do it. He started yelling out Bible type words. "God Bless! Father Son Holy Spirit! Hallelujah!" Well that worked!
Things were going well until he saw the sign up ahead that the bridge was out. It was a heck of a way down to the bottom of the gorge and suddenly he blanked out on the word for whoa. He pulled on the reins but the horse stiffened his neck and kept trotting along. The young man yelled out every word and phrase he could think of to make the horse stop. "Our Father who art in Heaven! Sweet Mother Mary! Jesus Christ! AMEN!"
The horse skidded to a stop with his front hooves inches from the edge of the cliff.
The man, shaking, wiped the sweat off his forehead. He looked over the horse's shoulder, down at the deep rocky gorge, and realized how lucky he was. He drew a shaky breath and said, "Oh, praise the Lord!"