The sun was rising over Big Cabin, Okla., when I pulled up to the drive-through window at McDonald’s and said, “Howdy.” My wife and I were driving north from Texas, and she, a Texan born and raised, could not stop laughing. “ ‘Howdy’?” she said, incredulous. “I’m from Texas, and I’ve never said ‘howdy.’ I’ve never even heard it said. Where does that come from?”

I can tell you where it comes from, the howdys in Oklahoma and y’alls in Texas, the ahlas in Israel and dai bastas in Italy. It comes from growing up feeling like an outsider and from training yourself, always, to fit in.

Back in 2009, that same Texan wife and I went to live in Berlin, immediately immersing ourselves in the culture. We rode the S-Bahn, ate doner kebabs and learned to say “genau” at all the right moments. (Honestly, if you just nod and say, “Genau!” you can spend your whole life in Germany without anyone suspecting you don’t know another German word.)

There was one local custom that left us baffled. We couldn’t understand the rules of decorum around public nudity. Passing Berlin’s Tiergarten at lunchtime, you might see a businessman walk into the park, take off his jacket and tie . . . his shirt . . . his pants . . . his underwear and, buck naked, take the sun for an hour before heading back to work. It was the same at the lake where we lived. Let’s just say there were great swarms of people with no place to pin their locker keys.