Idiopathic is an adjective that means of unknown causes.

The prefix of our word of the day, I-D-I-O comes from the Greek word meaning ‘one’s own’ or ‘private.’ And ‘pathic’ comes from the Greek word pathos (PA thos) meaning suffering. So an idiopathic condition is one that comes from an unknown source.

I’m no doctor, but Elena’s insomnia seemed to be idiopathic in nature. There didn’t seem to be any obvious cause of it.