This explanation is "straight from the Horse's Mouth
Some say this is originally a boast of confidence from a racetrack tipster
, who would say he gets his
from the horses
themselves—thereby assuring the bettor that the
info is the correct.
Another explanation is that a horse trader would persuade a prospective buyer
with all kinds of talk
about the animal, but for a clear measure of its worth, one can simply look in
the animal's mouth
. You can tell a great deal about a horse from its mouth.
, general health of the horse, and if it had been over reined.
If a horse
is unruly you have to rein it in a lot, and this shows in the horse's
mouth as well.