I’m not a historian or anything, but I was around and it was my peers that were getting these tattoos.

Shirts that show your tummy/lower back were also popular then (still are? 🤷‍♂️), so getting a tattoo there was a spot you could show it off while also keeping it hidden when needed.

IMO it really had nothing to do with sexuality until the joke started going around about “giving you something to read while doing it doggystyle,” and some people getting sexually suggestive ones lead to the phrase Tramp Stamp.