From what I’ve read, Im not sure he knew. I think the artist might have misrepresented its meaning back in the 70s. But the crescent moon above, with the Venus star, and the fish scaled legs apart and over her head, all have a very specific symbolic meaning. She is talked about in Revelation 17. 

 Thank you sir. As always you've given me the beginning of a promising rabbit hole. I'll be reading about it after the weekend 🤝