Question

This will be confusing, I’ll try to make it as clear as possible.
 
The term “Lady of the night,” what does it come from?
 
Specifically, does the “of the night” part suggest that the lady comes out at or inhabits the night?  
Or does it mean that it is the lady of this night but no other night as a reference to how you only see a prostitute once and never again?
 
I hope that was clear. Try going over the term in you head and thinking about how the same words can describe different things to get where I’m coming from.

If I’m remembering correctly, this is a shorthand euphemism for either a mistress or a prostitute, depending on the culture?
 
If that is the case, then it is a reference to the fact that it is usually easier to get away with sexual indiscretions at night*
 
_{*I think; It’s 2:40am here, thus I may be missing something when trying to deduce the etymology}

It’s a nice way of saying hooker i know that and it probably comes most peoples belief that prostitution only takes place at night in some cheap hotel,
 
Now I have a question, Why does my Avatar worry you?