Short answers, pulled from the story.
Anonymity describes situations in which a person's identity is unknown or kept hidden. The word was borrowed into English around 1600 from the Late Latin anonymus, which came from the Ancient Greek anonyomos, meaning without name, combining the prefix an- (un-) with the word for name.
The US Supreme Court has recognized rights to anonymous speech derived from the First Amendment. In McIntyre v. Ohio Elections Commission in 1995, the Court protected anonymous political campaigning, and in United States v. Rumely in 1953, it protected the right to read anonymously. However, 24 states have stop and identify statutes requiring people to identify themselves to law enforcement under certain conditions.
Alexander Hamilton, James Madison, and John Jay wrote The Federalist Papers under the pseudonym Publius. Their anonymous authorship allowed for open public debate about the controversial contents of the US Constitution, which historians argue helped the ratification process move forward.
David Chaum is considered the father of online anonymity. While a computer scientist at Berkeley in the early 1980s, he predicted that computer networks would make mass surveillance possible, foreseeing concerns that would not fully emerge on the internet for another 15 to 20 years.
Services like Tor and I2P encrypt data packets in multiple layers and route them through a network of relays. Each relay sees only its immediate neighbors, so no single point ever knows both the true origin and the true destination of the data, making them more secure than centralized anonymizing services.
Artists choose anonymity for several reasons: to avoid the cult of personality around their public image, to break into fields dominated by others, to protect themselves legally (as in the case of Banksy, for whom anonymity is vital because graffiti is illegal), or simply to live private lives. Examples include DJ duo Daft Punk, who maintained their personas from 1993 to 2021, and science fiction author James Tiptree Jr., who was actually a woman named Alice Bradley Sheldon.