Adamitism
The practice of going naked.
A few years ago, all sane people would have said that Adamitism was quite as mad as Anthropophagy. A banker walking down the streets with no clothes on would have been quite as nonsensical as a butcher selling man instead of mutton. (1929, G. K. Chesterton, The Thing: Why I am a Catholic).
Noun | ad-uh-mi-tism | 16th Century