I learned about this phenomenon through this article:
"Why won't 541,000 young Japanese leave the house?" (Emiko Jozuka, CNN, 9/12/16):
According to a Japanese cabinet survey released Wednesday, there are currently 541,000 young Japanese aged between 15 and 39 who lead similarly reclusive lives.
These people are known as hikikomori — a term the Japanese Health, Labor and Welfare Ministry uses to define those who haven't left their homes or interacted with others for at least six months.
The term was coined as early as the 1980s, but there is still much debate on how exactly this condition is triggered and how it can be defined.
Somehow or other, I found both the sound and the meaning of this word to be intensely beguiling.