The character of Maximus Decimus Meridius in Ridley Scott's Gladiator shows a man with nothing to lose, channeling his rage into coliseum fighting - but why did others call him "The Spaniard" as a nickname? The 2000 historical drama follows the aforementioned former general (played by Russell Crowe), who once had an undying allegiance to Rome and its emperor. That is, until Commodus (Joaquin Phoenix) kills his father in anger, gets away with it, usurps the throne, and has Maximus' family brutally tortured and murdered when he won't follow him as he did his father. The film is a modern masterpiece that has stood the test of time and there was even a Gladiator sequel planned at one point.
After losing everything, in his grief, Maximus--no longer a high-status general--is sold into slavery. Of course, he's then also quickly drafted into Rome's local gladiator games without choice. He's an underdog who's fighting for his life when he has nothing else to live for but the vengeance he seeks. But while he utilizes that rage to become an incredibly successful gladiator, as well as a crowd favorite, he's often referred to by a nickname that doesn't seemingly fit: "The Spaniard."
After all, Maximus doesn't appear to be of Spanish descent or have a Spanish name. And as far as his allegiance, he makes it clear throughout the film (though things change when Oscar-winner Joaquin Phoenix's Commodus takes power) that he serves Rome and Rome alone. But, as is explained during the movie's opening, the plot is set when Rome's empire sprawled from Africa to England. It also says that over one-quarter of the world's population was under Roman rule during this period. So, at the time, even if you called yourself a "Roman" or a soldier of Rome, it wouldn't have the same meaning as today. The empire had conquered a sizeable chunk of the world, and that included an array of different nations.
Also, at the beginning of Gladiator, which may yet get a sequel, Maximus says that his home is "in the hills above Trujillo." Today, Trujillo is an autonomous town in the Province of Cáceres, on the western side of Spain. Maximus is a loyal soldier, right down to his bones. And, at the beginning of the film, he reveals that he's been away from his family for over two years while faithfully fighting for the Roman Army. Clearly, his home is nowhere near the part of Germania where his character is during the movie's opening. This is also depicted via the long and arduous journey he has to take to get home once he escapes death and knows his family is in danger. He seems to have been geographically from Spain, prompting his allegiance to the empire it belonged to during the timeline of this epic from important sci-fi director Ridley Scott.
Additionally, Maximus is enslaved by merchants who seem to be of Middle Eastern descent. They look different than he does, and some of the other slaves do, as well. And he's then transported to what appears to be a Middle Eastern town surrounded by the desert--where he would, most likely, only stand out even more. "Spaniard" could be a sort of catch-all term for someone with a somewhat similar complexion to Maximus'. The nickname clearly sticks, but by Gladiator's end, it's Maximus' real name that crowds cheer.