Nan is actually a legitimate name (http://en.wikipedia.org/wiki/Nan) so if you're putting everything into upper case and not sanitizing, you're gonna have a bad time.
Null is also a legitimate name. When names are Anglicized from foreign languages there are often dozens of alternate spellings.
And dev is a common first name in India. Its a valid surname too, but that spoils the pun.
Somewhere in the world exists a poor soul named Dev Null.
Patio11's article "Falsehoods Programmers Believe About Names"