Border, LIMITS, and boundaries relate to a line between different jurisdictions or administrative districts, zones, village sections, town quarters, all areas with a separate set of laws, rules, and regulations. Borders are normally patrolled to limit unrestricted access across the lines, with gateways and low walls if within a city, checkpoints, document verification and medical inspection stations enforcing quarantines if necessary. Borders encompass areas ranging in size from a country down to a small neighborhood.
　「Inserted between」「filled orifices」as perhaps the anogenital distance within the perineum, which is the wall of muscle and tissue acting as the BOUNDARY, LIMIT of each mammalian female genital orifice, either as what is「between wet orifices」or,「to be between the walls within a filled and wet orifice」and is a fairly accurate representation of the entire SCOPE and LIMITS of a bonobo-human male's WORLD, or FIELD OF ENDEAVOR.
　Scholars explain this glyph is the space between rice paddies, depicting a limit to the water flow, however this interpretation of elements as the few inches of a dirt mound between rice paddies does not adequately account for the meaning MY WHOLE WORLD for most of us (even serfs), way back then or now…but the few inches between the front mons and backside sloping hills, is perhaps a different story and fits the elements too, as「person's erection with reciprocating motions plugging orifices」is perhaps the entire SCOPE and LIMITS of a human male's WORLD, or FIELD OF ENDEAVOR at least in the past if not now.
　ERATHEM are the boundary lines within rock strata formations found between different geological eras. Recall that when the material was first laid down, it was often settled mud slurry and silt or volcanic debris that later metamorphosed into rock due to heat, pressure, and time.
　Needless to say, the ancient Chinese knew that there was more to the Earth than just soil, dirt, ground…so this glyph likely was also referring to a more obtuse meaning, such as the perineum and related sphincters, with the associated BORDER LINE.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Unihan extended: person's name
EDRDG: world