What does idiopathic mean?

id·i·o·path·ic
Pronunciation: "i-dE-&-'pa-thik. Function: adjective. Date: 1669. Definition: arising spontaneously or from an obscure or unknown cause

From the Merriam-Webster Dictionary:

During my first year as a clinical medical student, I learnt many new words. Two of the most interesting were idiopathic and iatrogenic. Both are adjectives that doctors use as shorthand for a disease's cause. Iatrogenic basically means "it's our fault" (although the Merriam-Webster dictionary puts it less bluntly) and idiopathic basically mean "I don't know".

I have always found it fascinating that doctors use such complicated words to describe such simple concepts.

“[H]onest distinction between what is known and what is not appears again and again in fifth-centure [B.C.] thought, and is surely one of its chief glories.”
ER Dodds, The Greeks and the Irrational