Q: I’m curious about the origin of “fornication.” How did we get from arches and vaults to sex between people not married to each other?
A: In ancient Rome, prostitutes used to hang out in vaulted cellars such as those formed by the arches underneath circuses (arenas for sports and other spectacles).
Not surprisingly, fornix, the Latin word for an arch or a vault, came to mean a brothel, and fornicis, its genitive form, begot fornicari, to fornicate, and fornicatio, fornication.
As W. C. Firebaugh explains in notes to his 1922 translation of the Satyricon of Petronius, “The arches under the circus were a favorite location for prostitutes,” who “were always ready at hand to satisfy the inclinations which the spectacles aroused.”
The Chambers Dictionary of Etymology adds that “brothels in ancient Rome were often located in underground basements” and “prostitutes solicited their business under the arches of certain buildings.”
John Ayto, in his Dictionary of Word Origins, says early Christian writers identified “vaulted underground dwellings” with prostitution “and employed the term [fornix] with the specific meaning ‘brothel.’ ”
Interestingly, fornix is probably derived from fornus, furnus, or fornax, Latin for oven and a source of “furnace,” according to The American Heritage Dictionary of Indo-European Roots. Ultimately, the dictionary says, the usage comes from gwher-, a reconstructed prehistoric root meaning to heat or warm.
Standard dictionaries define the noun “fornication” as consensual sexual intercourse between two people who aren’t married to each other.
The Oxford English Dictionary’s earliest citation for the noun is from Cursor Mundi, an anonymous Middle English poem that the dictionary dates at sometime before 1300:
“Þis sin has branches fele … fornicacion es an” (“this sin [adultery] has many branches … fornication is one”).
The verb “fornicate” showed up in writing in the 16th century, with an early spelling of the infinitive.The first Oxford citation is from a 16th-century English-Latin dictionary:
“Fornicaten, or commit fornication or lechery, fornicor” (from Abcedarium Anglico Latinum, 1552, by Richard Huloet). Fornicari, source of “fornicate,” is the present active infinitive of fornicor.
The earliest example we’ve seen for the verb with its modern spelling is from the Douay–Rheims Bible of 1582: “Neither let vs fornicate, as certaine of them did fornicate, and there fel in one day three and twentie thousand” (1 Corinthians 10:8).