People with extreme or unusual beliefs, or handles that you turn to make something work.
From Middle Dutch 'krank' (weak, sick), originally referred to something bent or twisted, which evolved to mean a bent handle, then a person who is 'bent' or eccentric in thinking.
The same word describes both mechanical handles and obsessive people—because early people thought eccentric behavior was like having a 'twisted' mind, just like a crank is a twisted handle.
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