In one of George Carlin’s stand up specials, he does a bit about the different ways we can say hello or goodbye, such as Aloha. “They say that in Hawaii, of course, and that means both hello and goodbye, which just goes to show you that if you spend enough time in the sun, you don’t know whether you’re coming or going.”
He goes on to list off a bunch of different words and phrases that people use as greetings or valedictions. One of the phrases he talks about as a valediction is “Have a good one”. He then goes on to say that his response to that phrase is, “I already have a good one. Now I’m looking for a longer one.”
I never really used the phrase “Have a good one” before I saw that bit, but now I say it quite often in hopes that someone will give me the George Carlin answer someday.