The octothorp "#" - is s symbol that was originally used in mapmaking - representing a village surrounded by eight fields.
Read more fascinating facts about this and the origin of other symbols including this little gem about Prince:
In 1993, Prince’s dissatisfaction with his record label, Warner Bros., finally reached its peak. Despite his superstar status and $100 million contract, the Purple One didn’t feel he had enough creative control over his music. So "in protest," Prince announced that Prince would never perform for Warner Bros. again - this unpronounceable symbol would instead.
The symbol for the Artist Formerly Known as Prince combined three ancient symbols: the male symbol, the female symbol, and the alchemy symbol for soapstone, which was supposed to reflect his artistic genius. Prince retired the symbol when his contract with Warner Bros. ran out in 2000. Today, he is again Prince.