Variable text slowing site down?

This isn’t an urgent question, just more of a discussion. I noticed that a site I was building was really lagging at points where text was being loaded. After a little trial and error, I realized that it was due to the fact that I had given the text fields a variable name. I removed the variable name from the text field and it worked fine . . .

What is the reasoning behind this? Luckily in this case I don’t need the variable defined, but there are cases where it would be needed, so why is it slowing everything down? Is it because I have multiple instances of the text field with the same variable name . . . or?