Early humans「dwelled in holes of soil」hence penetrated and lived within SOIL WALLS, a rural lifestyle (僻):
「In north China, especially on the Loess Plateau, caves called yaodongs dug into hillsides have been the traditional dwellings from early times. …An estimated 40 million people in northern China live in a yaodong. Many people live in semi-recessed dugout houses in north-western China where hot summer and cold winters prevail.」
[ https://en.wikipedia.org/wiki/Pit_house 2012-07-02 ]
And in ancient Japan:
「The Early Jōmon is the first stage…of Japanese pre-history…[and] ranged from 10,000 to 300 BC…. This period saw a rise in complexity in the design of pit houses, the most commonly used method of housing at the time.」
[ https://en.wikipedia.org/wiki/J%C5%8Dmon_period 2012-07-02 ]
「Grounds of anal, genital, orifice penetration」as a PARTITION, LOW WALL located within a town or city used to delineate the red-lined districts from other areas. Relatively low walls and inner partitions are not designed as defenses against invading armies, particularly when located inside a town. Low walls are designed to restrict the motions of townsfolk and visitors, routing them toward the gateways where government patrols awaited to conduct mandatory medical inspections, measure the degree of symptoms, collect fees and bribes, constructed as a countermeasure implemented after rampant infectious pandemics of sexually transmitted disease occurred.
Moreover, literally refers to the sphincter and intestinal WALL, INNER LINING, INSIDE SURFACE with「feces, night soil」that surrounds a「penis, torture device」upon「anal penetration.」Top-left is clearly「anus」(buttocks hole) and top-right is「torture device」referring to penetration and punishment. The two top elements have all sorts of very wide-ranging connotations as might be expected, and in this case according to scholars:「tightly surrounding.」Anal penetration with「ground, earth, soil, dirt」(euphemisms, even in English, for「feces」) referred formerly to a completely enclosing wall on all sides. Whatever is used to penetrate an anus might likely be surrounded with feces on occasion, that is, surrounded by「soil」from the anal WALLS.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: wall; rampart
Japanese EDRDG: wall, inner lining, fence
Unihan extended: partition wall; walls of a house