The earliest discovered use of this symbol comes from a 1345 Bulgarian translation of a Greek chronicle, held today in the Vatican Apostolic Library. The symbol has been used in Catalan, Spanish and Portuguese to display a symbol of weight roughly equivalent to 25 pounds. This in turn is derived from Arabic expression of "the quarter". The symbol is used in various programming languages, although there is no consistent theme for usage. What symbol?
Answer to yesterday's question: "ARPANET". The name is a combination of "Advanced Research Projects Agency" and "Network". ARPA is a agency under the United States Department of Defense. Officially the network was declared operational in 1971. ARPANET was formally decommissioned in 1990 after private sector expansion and commercialization of an expanded worldwide network was confirmed, by which time the broader network was known as the Internet.
ARPANET was thus also the first proper network with its rules and etiquette. According to Wikipedia, Leonard Kleinrock was the first person to commit an "illegal" act, using it for his own personal reasons. Even if "illegal" is a bit spicy, it definitely was not in line with what was allowed. Against the rules, the first mass email was sent out in 1978 by Gary Thuerk.