malaria (n.)
Malaria is a disease carried by mosquitoes. The name is the Italian mala aria, bad air.1
It was named for what people believed caused it. Fevers were common around marshes, and the vapour coming off stagnant water was held to be what made people ill.12
The parasite was identified in 1880 and the mosquito was shown to carry it before the century was out. The air had nothing to do with it.2
The name did not change with the theory. We understand the disease now, and it is still called after an idea about air that nobody believes.1
Malaria is still one of the world’s deadliest diseases.