"Decorum," which is related to the term kairos, speaks to what is determined to be appropriate for a particular time, place, and audience. (But who gets to decide what's appropriate, you ask? Good question.)

More common, everyday uses of the word "decorum" are actually pretty close to the rhetorical term: it usually means (per Merriam-Webster) "propriety and good taste in conduct or appearance" with a tinge, in my mind, of snobby people trying to keep others in line by insisting they need to be a certain kind of polite. "Breaking decorum" generally means you're being loud and unruly, not following along, making a scene of some kind.

Arvatu and Aberdeen also note that too much of trying to be "appropriate" can be uninspired and, well, downright boring. They note that "optimal rhetorical decorum may call for an occasional dash of inappropriateness, to keep your audience from tuning out" and recommend working to find a balance (13).