etymologically, fornication derives from the same Latin root as oven:
namely, a fornix, -icis is simply a vault. As stone ovens were vaulted,
an oven was a fornax, -acis, from which the Italian forno="oven" is derived,
or the english furnace.
Also vaulted were cellars ("vaulted"=fornicatus),
and cellars were notoriously the locations of Roman brothels, the passive verb fornico, -or
came to mean "to whore"; and fornicatio, -onis was the ambiguously corresponding abstract noun
which later became the english fornication.
When in Rome, do as the Romans do.