That's a thing, right?!
I'm hoping that this isn't just me, but are there things which you've always thought were 'a thing', only to discover that they're unique to you (or maybe your family)?
Take PAT testing - when people around here said they were getting somebody in for this electrical test, I thought it was because our local electrician was called Pat. It was only years later when husband mentioned PAT testing at work did I realise that it wasn't the case, as he explained it stood for Portable Appliance Testing and was nothing to do with our go-to electrician!
Also, there's my making of black coffee for people. Now back when I was a temp during my holidays from Uni, I worked in an office where the accounts manager insisted on black coffee, several times a day, with cold water added to it so she could drink it straight away.
Not being a black coffee drinker myself, I thought this was how everybody made the beverage, and being the most junior person present just did as I was asked.
It's only very recently that I've discovered this wasn't the case. An important visitor arrived where I currently work and asked for a black coffee. I duly made one, presented it, and said I'd added some cold water to it - not sure why I said that, I think I was a bit nervous and trying to make a good impression! He looked slightly confused, but thanked me nonetheless, and on I went with my day.
Later on I was making another black coffee, this time for a colleague and I was adding the cold water as she walked into the kitchen. So I said to her about it, and asked her is that how everybody makes it, to which she laughed and said no. We asked more colleagues, and they'd never heard of it either, so it turns out that this one manager's black coffee order from 30 years ago shaped how I make the drink to this day.
But, in my defence, if you don't know, you don't know, do you?!