The advent of hot-air balloons allowed the first human beings to fulfill the ancient dream of venturing into the sky. The operators of these craft came to be known as "aeronauts", from Greek words meaning "air sailor", since the process was like to that of crewing a ship. But once airplanes came along and airships lost favor, the title of "pilot" became prominent and aeronauts were largely forgotten.
Then, in the 1960s, humans venturing into the new frontier of space created a new category of explorer. These came to be known as astronauts, "star sailors", which is fitting because Space Is an Ocean in the public mind. Russian spacefarers were given the separate name of cosmonauts ("universe sailor") to distinguish them during the heavy rivalry of early space exploration. As a result of these names, the suffix "naut" has become associated with space and scientific endeavor.
Those of us on the ground have long admired astronauts, who undertake tremendous risk in the performance of their job, spend weeks or months in an inhospitable environment, and have a sense of international camaraderie unknown to almost any other pursuit. As such, the "nauts" suffix has been used for fictional organizations, especially of a scientific, exploratory, or paramilitary nature (because most astronauts are inducted from the military due to similar skills being required), and to indicate that these groups are heroic and elite. While the specifics vary considerably, especially along the continuum of military vs. scientific purpose, the connotations are almost always positive.
The usage follows a specific format- a non-hyphenated compound word, which may or may not be capitalized, in which the first part has two syllables: somethingnauts. However, the trope title is Wiki Worded for clarity.
- The Expanded Universe novels for Red Dwarf refer to the explorers of humanity's early, disappointing, slower-than-light interstellar voyages as "stellarnauts".
- Les Thanatonautes by Bernard Werber. It means "death sailors" and it describes an exploration of the afterlife through controlled near death experiences.
- In The Colour of Magic, the Krullian explorers making the first foray off the edge of the Disc (or at least the first to be intentional and with a plan for coming back) are chelonauts (from "chelonian" meaning "turtle"). Presumably, the crew of the Kite in The Last Hero are also chelonauts, but the word doesn't come up.
- Chrononauts from Project Backstep in Seven Days; there are several individuals who carry the title during the course of the show. Parker is the main one, but throughout the series there's his friend Donovan who serves as "backup chrononaut" in case Parker can't be sent back for some reason (although he never actually goes on a mission). In one episode Parker comes across a hidden memorial to the chrononauts who came before him — he was just the first one to survive. In anther episode Robert Picardo plays a future chrononaut who visits the series' present from a distant future when they can travel more than seven days back. Olga was married to a Russian chrononaut before their time travel experiments got shut down and she transferred to the US's.
- The Argonauts, whose myth inspired the epic poem "The Argonautica" and the film Jason and the Argonauts, among many others, are called that for a very literal and straight-ahead reason: they're sailors ("-nauts") who crew a ship called named Argo (Greek for "swift").
- In Chrononauts, the players are time travelers tasked with strategically changing history to bring about their personal ideal timeline.
- The amusingly redundant Aquanauts and Hydronauts were two of several factions in the submarine-themed toy line "Aquazone" by LEGO. There were also the Aquaraiders, all three groups being oceanic explorers and deep-sea miners who were opposed by the Aquasharks and Stingrays, who were Submarine Pirates.
- The Astro-Viper from G.I. Joe: A Real American Hero is referred to as a "Cobranaut" as his specialty.
- Mixels has the character Nurp-Naut. He is an Orbiton (a space and alien-based tribe), with the Naut half of him being a wise elder, compared to the baby Nurp side.
- There was a line of toys in the late '70s called "Micronauts", which would literally mean something like "small sailors". They were little robots about 4 inches tall, with an assortment of vehicles and bases and so on.
- In Awesomenauts, the title characters are a group of mercenaries hired by two warring factions, the Ones and the Zeroes. Their task is to fight over drills on various planets excavating 'Solar', a precious liquid metal.
- In The Elder Scrolls lore, the Imperial Mananauts explored Aetherius during the heyday of the Second Tamriellic Empire (under the Reman Dynasty) in the late 1st Era in a "space race" with the Aldmeri Dominion. The Aldmeri used Sunbirds, ships somehow literally made from the Sun. (Which, in the ES universe, is actually a portal to Aetherius through which magic flows into Mundus, the mortal realm.) The Empire, on the other hand, used "Mothships", enormous Ancestor Moths bred, hollowed out, and flown into the void on strength of willpower alone. (Ancestor Moths have a special supernatural connection which also allows them to be used to somewhat protect mortal readers from the power of the Elder Scrolls, which is why the Scrolls are kept and read by the Cult of the Ancestor Moth.) The results of these expeditions have largely been lost to history.
- The space-exploring Kerbal aliens from Kerbal Space Program are called kerbonauts. Which is sort of bizarre, because they're just alien astronauts; we don't call human spacefarers "humanauts." As it turns out, the game never calls them kerbonauts (they live in an "astronaut complex.") The tropey term is a near-ubiquitous Fan Speak word derived from the game's tendency to put "kerb" in front of things (they live on a planet called Kerbin orbiting a star called Kerbol).
- The X-Nauts, the alien race from Paper Mario: The Thousand-Year Door.
- The Psychonauts are a group of highly trained psychics who travel the world having James Bond-esque adventures and generally keeping civilization safe from psychic threats. At least, that's the subtext- the actual game takes place at a summer camp for kids that teaches them to control their latent psychic abilities.
- Scribblenauts is a title-only usage, there don't seem to be any people in the games actually called "scribblenauts". The "scribble" part references the main character's notebook, which summons anything written into it.
- Xenonauts are an international military unit formed to counter the threat of alien invasion on earth.
- Policenauts is about a handful of police officers picked to keep the peace in an orbital colony.
- Parodied in Gunnerkrigg Court with Dr. Disaster's simulation games, which cast the students as "Spacemonauts" acting out a cheesy pulp sci-fi storyline.
- On his Atari 5200 video, the Angry Video Game Nerd wonders if the system's controller was meant to contact "fuckernauts".
- In The Adventures of Mark Twain, Tom Sawyer, Huck Finn and Becky Thatcher stow away on Twain's airship. Tom calls themselves "aeronorts", with Becky correcting him as "aeronauts".
- The Octonauts is an Edutainment Show (and a children book series) following the adventures of Funny Animals protecting sea-life. It got its name from their Underwater Base shaped like an octopus: the Octopad.
- The Canadian animated series 3 Amigonauts stars a Comic Trio of students attending an academy in outer space.