This is inspired by something from my own family: My first nephew and my dad. Nephew started saying something, dad responded, and dad has henceforth been known by that name (Tah).
"Va! Va, Va, Va!" exclaimed a 6-month old Von Trapp.
This caught the attention of the patriarch of the family, as he rushed over and scooped her up from his wife's arms.
"Yes, my love, that is me!"
"Georg, she is only babbling. And there needs to be a ti along the Va."
"I don't care. She knows who I am. And no need to sing!" He looked upon his daughter with adoration. She stuck her thumb in her mouth and leaned against him for a cuddle.
And so it went. The household learned quickly that "Va" from the youngest, if it was loud enough, would summon the Captain as if he was being ordered by an Admiral. While the lady of the house was exasperated on occasion, he was at her command when it came to snuggles, playtime, or just because.
Soon after, once she got her sitting skills correct, Kurt showed her how to slide paper under the study door.
The first time it happened Va opened the door.
"You're ruining it, Father!" he exclaimed.
The door slammed shut and the paper soon returned from whence it came.
After that, there were many paper-sliding contests, which may have hastened some crawling skills. Va could slide paper a long way, and after the first cries of frustration, relieved by Freidrich, she learned to do something about her Va's impertinent ways. Once again, the lady of the house was occasionally exasperated, but Va was as happy as a clam.
Years later...
Georg von Trapp was miserable, sitting in an anteroom of a church. While he was bathing in his misery a piece of paper slid under the door.
"I know that you are a GrandVa many times over." He chuckled at the name that had been suggested the first time as a joke but had stuck.
"But while today you're giving me away you will always be my Va, my one and only Va. Always."