Facetious popped up a few days ago, while I was too busy to deal with it, but I think I'll go on a kick to discuss words that we hear all too commonly and wonder whether they are being used correctly. So...
Facetious comes from the Latin "facetus" for "witty" through the French "facetie" for "jest". It is a rare word, indeed, that maintains it etymological roots. Probably because the word didn't originate in English until after the Middle Ages, c. 1590. And today, it still means "not to be taken seriously or literally" or "amusing or frivolous" as from lacking serious content. Contemporaneous to the evolution of frivolous, sarcasm came into being, from the Greek "sarx" or "sarkos" for "a piece of meat" and pre-Indo-European base "twerk" or "thwares" for "to cut", and by a further Greek derivative through "sarkasmos" for "to sneer" and then the late Latin "sarcasmos". Approximately 100 years later, sarcastic came into being. Why it took 100 years to get the adjective from the noun, we may never know. Now, this may seem odd, to get from rending flesh to sneering, but the idea of the sneer is the biting comment, harsh or bitter derision, akin to rending flesh not with an instrument, but with words. So, the difference appears to be that facetious is a comment that is cute and not hurtful, while sarcasm is irony intended to taunt. Of course, many mask sarcasm in the guise of facetiousness, so as not to offend (as much).
When he whistled at the girls on the street while leering from his convertible, it was easy to make a facetious comment that he was acting like a dog. When he whistled at the girls on the street while leering from his convertible, it was easy to make a sarcastic comment that he was acting like an angel. Too easy, and going to get boring quickly. Facetious and sarcastic both refer to speech. Since these words refer to the witty or biting remarks of people, it doesn't work with acts of people. Plaintiff's counsel's facetious conduct to twirl his pencil while in Court just doesn't make sense. Plaintiff's counsel's facetious remark about the witness' disheveled appearance as indicative of whether the witness cared about his testimony was not appreciated by the jury. I make sarcastic remarks about Plaintiff's counsel's lack of competence repeatedly in these posts. Again, much too easy. The only thing I will add is that the type of speech to which facetious and sarcasm apply is usually not formal. It's not a facetious statement or a sarcastic order. Both are off the cuff, not formulated or memorialized. Sarcastic has a sotto voce or behind one's back connotation to its usage since you should not be inclined to make hurtful statements deliberately to someone. Telling your adversary that she is your best friend is sarcasm. Telling your friend that the big pink bow she is wearing in her hair makes her look 10 years younger is facetious, and borderline sarcasm.
Both great words. Use them well. Use the comments which are the basis of the words sparingly.