I came across this phrase today while doing a lookup on 背中.
I checked several sources, and all listed the meaning, amongst others, "to teach with one's back". It seems related to learning by example, such as when growing up how you learn from your parents or older siblings. Things related to manners, morals and in general "how to get along in the world".
But as far as I searched, I could not find good example sentences using this phrase. I found some examples here
but these seem to be general teaching references in a historical setting.
So I am wondering if this phrase has a historical background, and also where the "back" reference came from. Learning while watching someone from behind?