* Candle: A source of light made from wax.
* Candid: Open and honest, not hiding anything.
* Candidate: A person who is considered for a position or office.
* Incandescent: Emitting light as a result of being heated.
* Candor: Frankness and honesty of speech or writing.
* Incandescence: The state of being incandescent.
You'll notice that most of these words relate to the idea of light or brightness, which is tied back to the root meaning of "cand".