Facetiousness is the noun: the habit or quality of making those poorly timed, try-hard jokes. You can talk about someone's facetiousness, or the facetiousness of a remark. It names the behaviour, not the person. It is still a fairly formal, slightly judging word — the kind you use when you are tired of the joking, not when you are laughing along. If a room has gone quiet and one person keeps needling it with clever remarks, that is facetiousness.

插科打諢；不正經搞笑（指這種態度或口氣，不是稱讚）