• zyzzyva •
It is a developmental phase. The child associates "having the last word" with dominance. Since it is their job to grow up and have dominion over their environment, most kids try it out for size. They are just doing their job.
Most kids eventually realize that "last word" is a symptom of power rather than a source of power. And they grow out of it.
A few do not. They never seem to figure out that relying on "last word" is an admission of a power disparity. It is verbal guerrilla warfare. Never holding ground, conversationally, and turning it to a productive use. "Last word" is a war of nagging attrition. The more powerful party rarely chooses nagging wars of attrition, of burning down the house.
Avoid negative people
Ahhh! Words to live by. Except when it is not possible. Maybe they share your work cubicle, your fire station, your car pool or your family dinner table. What to do?
That is when it is handy to have a good vocabulary. Just do what I do. Firmly announce:
Pronunciation: zi-zê-vê • Hear it!
According to alphaDictionary.com "zyzzyvva" is the last word in the American Heritage Colligiate dictionary. It is also a species of life sucking weevils which somehow seems appropriate when discussing people who insist on trying to have the last word.
And now they cannot have it because you just claimed it.