A man cave or manspace, is a male retreat or sanctuary. In a document where Ptaah is describing the residences on Erra, he describes a small building outside of their homes, where only the man is permitted, and the woman may not go. In another document Quetzal describes a vehicle collection that he personally keeps.
The term "man cave" is a metaphor describing a room or space inside or outside of the home, such as a specially equipped garage, spare bedroom, media room, den, attic, office, wood shed, tool room, basement, allotment, barn, warehouse, lock-up, bunker, boat etc., etc. where "guys can do as they please", without fear of upsetting any female sensibility about house decor or design.
While a wife may have substantial authority over a whole house in terms of design and decoration, she generally has no say about what gets "mounted on the walls" of a man's personal space. Since it may be accepted that a woman has input on the decoration of the rest of the house, a man cave or man-space is in some sense a reaction to feminine domestic power.
Paula Aymer of Tufts University calls it the "last bastion of masculinity". The phrase is thought to come from the 1993 publication, 'Men Are from Mars, Women Are from Venus'.