Kook: A person regarded as strange, eccentric, or crazy. Also a hacker & online slang term used to describe a regular poster who continually posts messages with no apparent grounding in reality. Different from a "troll", which implies a poster who knows better, kooks really believe what they write, to the extent that they believe anything.
Kluck: Also: "Cluck" or "clucker". Street slang for a crack fiend, meth-head or other hard-drug addict.Also used as a verb meaning "to trade something for drugs", as in "Slim clucked his DVD player for a rock".
Klan: The Ku Klux Klan (KKK), a 19th & 20th-century US racist and antisemitic white supremacist organization comprised primarily of lower-class disgruntled farmers and moonshiners who worship an ancient Jewish man-god.