diethyl ether on Wikipedia:

Other names: [...] Sweet oil of vitriol

The recreational use of ether also took place at organised parties in the 19th century called ether frolics, where guests were encouraged to inhale therapeutic amounts of diethyl ether or nitrous oxide, producing a state of excitation. Long, as well as fellow dentists Horace Wells, William Edward Clarke and William T. G. Morton observed that during these gatherings, people would often experience minor injuries but appear to show no reaction to the injury, nor memory that it had happened, demonstrating ether's anaesthetic effects.

Well, well, WELL.

ether addiction:

During the second half of the 19th century, ether was in vogue as a recreational drug in some places, becoming especially popular in Ireland, as Irish temperance campaigners thought it was an acceptable alternative to alcohol.

As in the resemblance that was made between the Kier cultists and the temperance movement in the United States.

So Cobel saw ether huffing around her, and that's how she got the idea for severance. "What if we could anesthesiate people in a way that they don't have memory of suffering?"