I came late to this thread, and I have not read all the responses, so please excuse me if what I say has already been mentioned.
Grounding is about 'returning back to earth (ground). It is about re-connecting with a deeper reality of who we are as a human organism walking on this planet. It has profound spiritual and psychological implications, much like pressing the rest/default button in our biological system.
IT IS HUMBLING. The word humble comes from the word humus, which means earth/ground.
Humbling is about returning to earth (not in some mental cloud of self importance).
There is a famous Japanese garden with a tea-house. Many important meetings, even for international politics, have been held in this tea house. To gain access to it is to go through a very low opening in which requires a person to crawl on their hands and knees. Those attending the meeting will also realize that they must return the same way. This 'grounds' all the people, for a while anyway, to the same level.