What Was Something You Thought Was Normal Growing Up, But Later Found Out Was Strange?
We all had some strange habits growing up.
As a kid, it can be hard to tell the difference between something everyone does and something that's just a quirky family habit/tradition.
Warner Bros. Television
Take for instance this story from Reddit user LearnedButt, who discovered that his bathroom habits were a little… unique.

imgur.com
I'd recommend reading the whole thing, but tl;dr: A man asked his friend if he could borrow his "poop knife", not knowing that most people didn't grow up using a "poop knife".
Maybe you had an eating habit that you thought everyone else also took part in.
growing up i always put chocolate syrup on my cereal and i honestly thought it was normal and everyone did that until i got to college
Or perhaps your family had a phrase that you assumed was in common usage.
growing up, my mom would jokingly describe food as "testy and malicious," bc it sounds like "tasty and delicious." I thought this was normal