DNS is the addressing system for the Internet, it's certainly at the "core" of the Internet. I'm not sure whether it matters whether DNS is a "resource" or not, but it is certainly important to all operations of Internet applications. It's not about whether domain names are "words" or not -- they serve a critical identification and filtering function, and who controls that function is what is at issue here. The less central the control, the better, ad ICANN places itself at the very center thus it ought to minimize its control to matters it can actually address effectively like technical/operational criteria. Your use of the word "core" is not what is meant in this context, and the word "words" is too non-specific to have useful meaning here.