A concept originating in Japan, whereas
social interactions and dealings were considered more intimate and relaxed when they took place within a communal "onsen", or public bath.
This concept is still in some practice today, as when a business agent will meet a potential client for dinner, or drinks, or on a
racquetball court.
It has also evolved to define a situation of intimacy derived from the touch of skin, or close proximity thereof, as in a mother and child bonding from birth.
In Korea, as well as some other places, it has come to also mean
sexual contact, heavy petting, and related activities.