Rhaphanidosis is the act of inserting the root of a plant of the raphanus genus (commonly known as horseradish) into the anus. It is reported to have been a punishment for adultery in ancient Athens of the 5th and 4th centuries BC. There is some doubt as to whether the punishment was ever enforced or whether the references to it in comic plays (such as the debate between Right and Wrong in The Clouds of Aristophanes,[1]) should be understood as signifying public humiliation in general.
In order to be allowed to apply rhaphanidosis to an adulteror, one must catch the man in the act of adultery with one's own wife, in one's own house. Rhaphanidosis was not the only penalty available; sodomy by mulletfish was common as well, or the man could simply be killed on the spot. Following this, the adulterous wife would have to be divorced.
Later classical references to the punishment include Catullus 15 where percurrent raphanique mugilesque (both radishes and mullets will run you through) is threatened against those who cast lascivious eyes on the poet's boyfriend.
The classification of the raphanus genus is currently not well agreed upon, but during the antique and medieval times, all kinds of horseradishes and similar plants were commonly included in this genus.