The name "mara" might come from a creature in Scandinavian folklore. When people had nightmares they said that they had been ridden by the mara (the Norwegian word for nightmare is "mareritt") who took the shape of a woman.
In Greek culture the name is "mora": an elderly woman who visits people while they sleep and has much to do with sleep paralysis.
In Buddhism, Mara is the name of a demon that tries to sway Prince Siddhartha (Gautama Buddha) from the path of enlightenment by sending (some say they went of their own will) his daughters to seduce him. (They failed.)
In Hebrew, "mara" means "bitter," which carries the implication of "strength." In the Bible, the mother-in-law of Ruth, Naomi, claims the name Mara as an expression of grief after the death of her husband and her sons.
The movie references the deaths of "hundreds of Hmong" in 1977. These deaths were most likely the result of arrhythmic cardiac disorders, such as Long QT syndrome, Brugada syndrome, or similar conditions. Wes Craven was inspired to create Freddy Krueger, who was also referenced in this movie, after reading an article about these unusual deaths.