Namor's name could have been derived from a combination of factors within the comic's lore. It might be related to the language or culture of the underwater civilization he comes from, or it could have been a creative choice made to make him stand out among other characters.
Namor's origin story is fundamental to his character in Marvel. His mixed heritage means he has always had to straddle two very different worlds. In Atlantis, his human blood made him different, and on the surface, his Atlantean side made him an oddity. This led to his proud and sometimes arrogant nature. He feels a strong sense of loyalty to Atlantis as it is his mother's homeland, but his human side gives him a curiosity about the surface world. His origin story has also made him a powerful figure, and his character is defined by his struggle to find his place between the two worlds, which often results in him taking actions that are not always in line with traditional hero or villain roles.
Namor isn't Asian in the comics. His character has been established with a specific ethnicity and origin that's not Asian. This has been consistent throughout the comic series.
Namor wasn't Mayan in the comics. His character has a distinct and established backstory that doesn't involve being Mayan. Usually, his heritage and roots are presented in a specific way within the comic universe.