This sounds funny, but the biggest used nickname is America. It is short for "United States Of America"
I believe the answer is: Grief
In psychology, grief refers to the process of coping with the overwhelming emotions that created when we loss someone that we care about.
During this process, most individuals would most likely unable to use the social and cognitve skills normally, which would affect their overall behavior
The Chinese found out that they could use coal to heat things and make steel.