Facetiousness is a quality of joking around, or treating serious subjects in a humorous way. Your facetiousness might make it hard for your friends to take you seriously.
A stand-up comedian's facetiousness can be seen in her tendency to be sarcastic, or to playfully joke about serious issues. The facetiousness of a play might make critics describe it as a farce or a parody. Facetiousness can come across as lighthearted humor, but it can also be a little bit inappropriate or bitterly ironic. Facetiousness comes from the French facétie, "a joke," with its Latin root word, facetia, "jest or witticism."