Miasma is from a Greek word μίασμα meaning 'pollution' or 'stain'.
In Greek mythology the opposite of Miasma was Katharmos meaning purification.
Apparently this was a big deal in Greek religion, from the blurb for the book 'Miasma' by Robert Parker.
Most of the commonly read Greek texts address "pollution". The pollution theme appears in tragedies, historical texts, and political oratory. Purity is a constant concern in ritual texts, and Greeks underwent many small purifications in their everyday lives. Certain archaic religious movements even made "purification" the path to felicity in the afterlife. First published in 1983, Miasma is the first work in English to treat this theme in detail.
Really the only other place you'll come across much mention of miasma these days is in that most misunderstood genres of music, metal and its myriad sub-genres. Miasma was the name of a now defunct Austrian death metal band, a possibly real Canadian black metal band, and is the title of an album by a melodic death metal band from Michigan, The Black Dahlia Murder. You can check that out on YouTube, although I couldn't quite make out some of the lyrics. Okay, I couldn't make out any of the lyrics but it did make me laugh. They also have a track called 'Statutory Ape' which is a great name for a song.
It's also just a really good word. It is generally pronounced my-asma, and a dictionary will give this as the pronunciation but I've seen it suggested that the Greeks would have pronounced it me-asma. Any Greek scholars like to confirm this?