"petite mort"

A celtic stone. The Cross-in-Hand would have looked something like this
Creative Commons Attribution Share AlikeA celtic stone. The Cross-in-Hand would have looked something like this - Credit: Hugh Mortimer
Although this French phrase, which translates literally as "little death", is often used to refer to orgasms, it has a wider meaning. In this context, Hardy uses it to imply that a part of Tess has died on hearing the man's gruesome tale and connecting it with the oath that she was forced to swear on the spot.