Uterine contraction > Labour and pregnancy, In orgasm https://en.wikipedia.org/wiki/Uterine_contraction
Birthgasm https://en.wikipedia.org/wiki/Birthgasm
In terms of evolutionary origin and adaptation and natural selection (mutation, crossover, selection), all amniotes (reptiles, amphibians, mammals) have a clitoris.
Animal clitoris https://en.wikipedia.org/wiki/Animal_clitoris
The idea of it being a pain killer for birth but requiring a vibrator is interesting, because I don’t think any culture developed clitoris stimulation as a child birth helper. If it did help I would expect it to change birth outcomes and thus being a source of positive selection.
The only thing that bothered me is that gender affirming is in fact an amputation, because they gave their clitorises to science. It even took me a while to understand what the term “gender affirming surgery” meant.
Although not essential for survival, pleasure seems to be programmed in us as a species, so the body evolving this to give women the balance of a complex pleasure organ to make up for the pain — in so many levels — they go through during birth.
So maybe nature was like “they suffer a lot during birth and pregnancy, let’s give them a clitoris that gives them REALLY good pleasure that the male counterpart won’t be able to ever experience or comprehend.”