The term [facet] is English and derives from the French word [facette] meaning "a small face". The French term is itself derived from the Latin [facies], meaning "face".

The term facet in anatomy is used to refer to a small smooth surface, usually an articular surface. Another use of the word, still meaning "a small face" can be found in the jeweler's term [facet] used to describe one of the many small surfaces in a diamond.    

In spinal anatomy, the term “a facet joint” is most commonly used, but the term should be pronounced with the accent on the first syllable as in “fácet”! And just to be a bit more correct, the proper term for a so-called “facet joint” is “zygapophyseal joint”. This term is one of several medical terms that are used and/or pronounced incorrectly.