It's in the public eye more than ever. With social networks such as Facebook and Twitter (and their related integrations on a myriad of other websites), the mysterious symbol has arguably become a part of the human consciousness either due to active use or latent awareness. Why does the # glyph have so many names? Where did it originate?
The British call it the "number sign" since "pound sign" could easily be confused with their currency. As such, it is often spoken as the word "number" when read aloud. Its newest name is the hashtag, but the oldest is probably the one the Brits eschew. "Pound sign" arose from the abbreviation for weight--lb meaning "libra pondo" or "pound by weight" in Latin. To denote that the two letters aren't part of a word, many Latin scribes would cross the top of the two letters with a line. Eventually, the # was born.
Although "pound sign" may be the first widely-used title for the # symbol, octothorpe is its official name. Lab technicians and scientists developed a new word to christen the symbol's importance on the telephone keypad. In the 1960s, Bell Laboratories added the octothorpe so that the telephone operating system would be able to recognize instructions. "Octo-" was inspired by the number of ends within the symbol, and the rest is rather unclear. The three most popular stories are that a lab employee named it after the Olympian Jim Thorpe, the suffix is simply a nonsense word, and that "thorpe" is an Old Norse word meaning "field." The latter example would make "octothorpe" mean "eight fields," which has significantly more etymological substance than any other surmise.
The "hash" prefix that is very popular today could actually be traced back to descriptions of military stripes on uniforms as early as 1910. About 70 years later, the word has become a lot more civilian-friendly... and considerably more social.
What do you call the # symbol?