When my brother was born I was two-and-a-half years old. As he began learning to speak I could understand him when the grown-ups couldn't. Looking back I realize that was because the adults were trying to decipher his attempted words, but I tuned in to his intonation patterns and body language.
Not long afterwards we moved from New Jersey to California and I was amazed at the differences in the way people talked. Instead of pushing baby carriages they used baby buggies. Instead of sitting on sofas people in CA sat on couches.
One day we were visiting some of my mother's friends when the older kids told me there was a whale on the kitchen table for me. I assumed they were teasing me, especially since they were all eating ice cream and didn't offer me any. Later an adult asked me why I'd let the whale melt instead of eating it and I discovered it was a chocolate-covered ice cream popsicle. "Whale" was the brand name. In the neighborhood where I'd lived before we called that kind of treat winter popsicles because the little neighborhood grocery store only had them for sale during the cold part of the year. In the warmer months they sold summer popsicles, the kind made of fruit-flavored ice.
The difference in names was so interesting it almost made up for my disappointment in not getting to eat the delicious thing.