What is the purpose or meaning of the crescent moon found on an "outhouse" door?

[quote]Level with me: you've never actually seen an outhouse with a half-moon cut into the door, have you? Neither have I, despite several decades of camping trips. I'll bet the same goes for just about everybody else. The idea that outhouses always have moons on them has been perpetuated largely by several generations of cartoonists (e.g., Al Capp), probably none of whom ever saw one either.

The only reference I can find to the practice is in Eric Sloane's The Little Red Schoolhouse: A Sketchbook of Early American Education. Discussing 18th- and 19th-century schoolhouses, Eric writes: "The woodshed was often a lean-to attached to the schoolhouse, but the most accepted arrangement was to place it between the schoolhouse and the privy, with a fence separating the boys' entrance from the girls'. The ancient designation of privy doors was to saw into them a sun (for boys' toilet) and a moon (for girls' toilet)." Eric has supplied a sketch of both versions, showing the familiar crescent moon for the girls and a radiant sun for the boys.

By way of corroboration, I note here in my manual of semiotics that the moon "is usually represented as the feminine power, the Mother Goddess, Queen of Heaven, with the sun as the masculine." Isn't that just great? All this time you thought you were in there just doing your business and now it turns out you were participating in a pagan ritual.

Why cartoonists picked up on the moon rather than the sun as the universal symbol for outhouse is hard to say. But knowing cartoonists I'd guess it has something to do with the fact that the radiant sun is hell to draw. The reason there's a hole in the first place is a lot simpler: it provides ventilation.
https://nodum.org/hearts-and-moons-on-outhouse-doors/

The cresant moon for girls, and the sun or star for boys, precedes the comic strip. By the 19th century the meaning was lost, and many only had the moon. The design(s) was carved high on the door for privacy, and to provide light and ventilation. A friend prompted this research, and said he had seen modern "port'a'potties" with cresant moon decals on the door.(Going back as little as 20 years ,I have seen outhouses that were "new construction", and my "x" who is a visiting nurse, had client's who had to go to the stream to get water, and heat it on the stove, so she could wash her hands.
www.jldr.com/ohindex.shtml

...because most people were illiterate, symbols were used on the outhouses to show which was "his" and which was "hers". Pictures of the sun and moon were the obvious choice. From ancient times, the "sun" had been a symbol of all that was masculine and the "moon" of all that was feminine. -- from wikipedia.org https://en.wikipedia.org/wiki/Outhouse

Same building...different entrances.

The woodshed was often a lean-to attached to the schoolhouse, but the most accepted arrangement was to place it between the schoolhouse and the privy, with a fence separating the boys' entrance from the girls'. The ancient designation of privy doors was to saw into them a sun (for boys' toilet) and a moon (for girls' toilet).

https://www.bnd.com/living/liv-columns-blogs/answer-man/article47055115.html

This link presents two theories:
1. Lighting only.
2. Crescent moon represented the female in colonial days. Sol was the male counterpart (star or sun burst).
http://www.jldr.com/faqs.html#moons

Early outhouse builders were purely no nonsense folk who would use old leather scraps for hinges and made a cutout shaped so a fella could stick his hand into in which to use as a "door knob." Expensive hardware usually wasn't used on a building which would probably be replaced and was placed out of sight. This crescent shaped cutout was so matter of fact that folk back than never bothered to write it up although if folk saw a building with such a crescent shaped cutout, they knew what that building was for. More permanent structures on the homestead, were more apt to have hardware. Over time, as hardware come to be cheap and more outhouses were built with clean-out flaps, making them more permanent, there no longer was a need to use the cutout as a door knob but that practice was so universal in the past that a representation of it was placed somewhere on the structure, as a sign to identify this structure. As time went by rustic carpenters become scarce and folk had become farther away from their roots, so folk just made guesses on this subject.

The most popular guess assumed few colonists could read but for some reason attributed the crescent moon symbol to lady folk and therefore whenever a colonial saw one, thought of lady folk. Problem with this thought, is that almost all colonial folk could read, having read the Bible from early age, attended schools, read newspapers and so on. In fact democracy thrives in a well schooled society.

Eric Sloan's explanation sounds basically like what many school teachers would do to teach their students classics. Most antique privies I've restored had windows above the sight line, providing plenty of light and ventilation. Old folk would never have used the crescent shape for light or ventilation. It does a lousy job. My reference goes back to standing jakes dating back to 1736.

https://www.bullhillworkshop.com/about-the-moon-crescent/