A good hiding
To be given a good hiding...
I am an English teacher and I tend to use a lot of idiomatic expressions...
I believe that this comes from 'hide', to skin an animal, therefore a good hiding refers to the apparent result of the beating...
Does anybody know the true meaning?
It's rather simpler than that. There is a (now rare if not obsolete) colloquial verb "to hide", meaning "To beat the hide or skin of; to flog, thrash". A "hiding" is simply a session of this activity.