In any programming language, there are a group of words called ‘Reserved Words’ that are set aside for specific purposes within the given language. The developer needs to keep this in mind when they are writing code. If they use one of these reserved words within their code where it is not intended to be used, their programming could yield odd results.
// This line of could would return the location of the current page.
var x = location.href;
So if you use the word, ‘location’ in your could, you could inadvertently send the end user to a non-existent location, thus breaking your code.
Here is a link to some reserved words.
Now, beyond the use (or non-use) of reserved words is the concept of naming things intelligently. Please, for the love of all the sanity of developers everywhere, please name things that make sense. What I mean is name your pieces of code in a manner that is logical. Name variables with names that make sense. If you are getting a name from the end user, perhaps name it userName. Do not use any random or non-sensical verbiage. This practice goes hand in hand with proper comments.