Why didn't you just ask for help from someone who is a native speaker?

And yet this is in perfect English

You were writing a program? std is a key word in many programming languages, so maybe they were just laughing at the fact that you used a key word for your variable name.

Maybe your supervisors were huge nerds who found it funny that you would use a state transition diagram in a Gaussian distribution. I hope you weren't trying to program an accident information display system. In other words, if you browse through the Oxford Dictionary of Abbreviations, you'll see ambiguous abbreviations on every page, some of them with ten meanings or more. Your supervisors should have outgrown grade school humor.

I would laugh with them like I did it on purpose so I wouldn't look bad just funny at the wrong moment

That's a bit immature of them. I am a statistics student and I have seen standard deviation abbreviated as STD before. Then again most of my professors are not native English speakers either...

/awkweeeeerd.

Oops, this was supposed to be a reply.

are math symbols not universal?

I'm an astrophysics student who uses statistics in virtually every class, and as far as I can tell, "std" is a very common abbreviation for "standard deviation". In C++, std is the keyword for "standard", so NEVER use std as a variable name.