「Soil, feces」and「vagina」as the ENVIRONS that are「surrounding areas」or「areas that do the surrounding」of a male appendage…see the Used-In glyph 垌 meaning a「place for planting seeds」and farming is not done well in the wild, wild, wilderness…nevertheless,「feces beside vagina」does suggest a bit of wandering off the beaten path and engaging in WILD BEHAVIOR and actions, a wild place within valleys among hills.
　Within a populated area many thousands of years ago, and today too,「grounds for vaginas」referred to the red-lined prostitution districts that sprang up around and surrounding the ENVIRONS of a lord's castle (later, becoming cities) conveniently located near the wealth and most-desired clients with money.
　「Ground, soil」with「difficult to access, crossing the border of no return, no going back again during the current session」the「doorway to the neighboring spot」and so on refer more simply to a one-on-one situation involving both sides and entering the「soil section.」References to THE WILDERNESS literally as WILD AND CRAZY TIMES AND PLACES, the natural condition as described by the definition of the English word rather than to anywhere uninhabited, per se:
　「1. An unsettled, uncultivated region left in its natural condition, especially: A) a large wild tract of land covered with dense vegetation or forests [many 木 woodies]; B) an extensive area, such as a desert or ocean, that is barren or empty; a waste [vast wasteland of fluid flows]; C) a piece of land set aside to grow wild [literally walled-off and segregated from the rest of the city, with its own rules and regulations]. 2. Something characterized by bewildering vastness, perilousness, or unchecked profusion: the wilderness of the city, the wilderness of counterespionage, a wilderness of voices」
　　[　https://www.thefreedictionary.com/wilderness 2014-11-20　]　

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)
Chinese: environs; wilderness
Unihan extended: wilds
EDRDG: wilds