Avraham Avinu's Kippah

I occasionally have to buy Junior a new yarmulke from the seforim store, because his clips come loose in school, and then he loses his kippah. And so  shortly before Pesach I went to the store and purchased his a new light-blue kippah. After buying it, I noticed an inscription inside of it, stating that it was from the Bat Mitzvah of Plonis, in June 2008.

Amused, I showed this to a few people. (Some suggested returning it for a refund, or discount, but I did not see the point.) And Junior got wind of this.

The next day, when bringing him to school, he proudly announced about his kippah (another one, in black leather) that it was really, really old. (And not merely from 2008.) In fact, it was so old that this was the kippah first worn by Avraham Avinu.

I expressed appropriate astonishment and appreciation of the wondrous nature of his kippah. I did not want to insist the Avraham wore no kippah. (After all, the pasuk says "Lech Lecha". Would he have gone out of his land, birthplace, and father's house, without wearing a kippah?!) And there is some value to the imaginations of childhood. But I did want to expose him to the idea that perhaps this was somewhat anachronistic. And so I mentioned that I wasn't certain that Avraham wore a kippah.

His reply was that of course Avraham wore a kippah!
"How so?"
"Well, Avraham was the first Jew, and Jewish people wear kippot!"

A good proof, but I explained how people dressed differently in different times and places, and that no pasuk lays out a Biblical requirement to wear a kippah, and so it was quite possible that he didn't wear a kippah. He was not convinced. And a girl in the walking pool thought about it and said that she is going to her grandfather's for Pesach. He is a rabbi, she explained, and so she would ask him so that he could resolve this.