An intended derivative and omission of “nice” from the
far more colloquial “have a nice day”. Said as a bare minimum “polite” response when one is aggravated or feels sleighted.
It’s polite in the sense that it intuitively sounds like have a nice day and
basically implies that the speaker cares enough about the recipient that they hope the recipient doesn’
t die...at least for today.
However it’s also borderline rude, and could be perceived as a way of indirectly telling someone to fuck off, depending on the context. It intentionally omits “nice,” implying that the speaker is either in a general not-nice mood, or does not care about the recipient enough to wish them a nice day per se. Still more graceful than telling someone to
piss off, as you can always feign
ignorance to any malicious intent.