reserved word 
noun Computing
A word in a programming language which has a fixed meaning and cannot be redefined by the programmer.Well, in addition to scanning for offensive strings, some names contain reserved words, or keywords goes the theory....
- It's common to reuse components, so once found, they're saved as handy property values on the klass object-class is a reserved word in JavaScript.
- If we don't want this behavior, we can make a variable local to a function by preceding it with the reserved word typeset.