expression
even an unruly horse can be tamed
Proverb meaning that even a difficult or wild person can be brought under control with the right approach or person. Literally, 'even the horse at the back door has a matching bit'.
「背戸の馬も相口」という諺がある。
There is a proverb, 'even an unruly horse can be tamed.'
The exact origin is uncertain. The phrase uses the image of a horse at the back door (背戸の馬) and a matching bit (相口/合い口) to express the idea that there is a suitable partner or method for everyone, even the difficult.