Idiopathy

A disease whose cause is unknown. From the Greek word idios, meaning one's own.

Source: The American Heritage Dictionary, 4th. ed.

Id`i*op"a*thy (?), n.; pl. Idiopathies (#). [Gr. ; proper, peculiar + , , to suffer: cf. F. idiopathie.]

1.

A peculiar, or individual, characteristic or affection.

All men are so full of their own fancies and idiopathies, that they scarce have the civility to interchange any words with a stranger. Dr. H. More.

2. Med.

A morbid state or condition not preceded or occasioned by any other disease; a primary disease.

© Webster 1913.