Thanks for commenting.
That's how euphemism works.
People use an innocent term to substitue something else that is considered taboo.
Cowherd/牛郎 is a popular romantic figure in Chinese mythology, which is why it is used as an euphemism for male sex workers.
If you go on Urban Dictionary, you can find alternative meanings to a lot of seemingly innocuous terms. (I was shocked when I looked up the meaning of salad, especially of the tossed variety.)
One can read the D&D rulebook and snicker every time the word "blow" is used.