Nickname is a fictitious name used by an individual as an alternative to his legal name. Usually, pseudonyms are names invented by writers, poets, journalists, artists, and other famous people who do not want or cannot sign their own works. The pseudonym samuel clemens (Mark Twain) gave himself pay tribute to was his days as a riverboat captain.
I believe the answer for the above question is his days as a riverboat Captain. A pseudonym is a fake or fictitious name for example, an authors pen name, or a name that someone might use on the internet that is not their real name. A pseudonym is a made-up name used by a person to conceal their identity. It is most commonly associated with writers and are referred to as "pen names". A famous example would be Samuel Langhorne Clemens who is more commonly known by his pseudonym Mark Twain.
With terrorism a National security faced by the united states would have definitely been 9/11 when members of Al Queda took down the twin towers. Then for Nuclear weapons is that North Korea is threatening to use nuclear weapons
