If I change the variable name, I get a 'type error'

I'm trying to practice Python in RM by linking the ipynb script.

However, the variable name of the sample data is not what I want, so I am trying to change the variable name and print it.

There is no error when the variable name is not changed, but an error occurs when the variable name is changed.

I just changed the variable name. What on earth does this error have to do with it?

I am attaching the code I wrote and the error message.