Written by Kyuss guitarist Josh Homme, "Demon Cleaner" finds frontman John Garcia singing about purging the demons from his system. The song could be interpreted different ways, but it's really about brushing your teeth.
Dentists and oral hygiene were a big deal for Homme, who used to have nightmares about having his teeth pulled. So the song does relate to his personal demons, but it's also quite literal: the line "I get the back one,
Important they'll always stay," is about brushing your molars.
Garcia, however, would interpret Kyuss songs as they related to his life, and he encouraged listeners to do the same. "If you try to get something deeper out of that from that song, I think that's great," he said in our 2014 interview
Kyuss didn't print the lyrics on their albums for this very reason: they wanted listeners to hear it through their own ears.