ill-ness / ĭl-nĭs
1. a disease or period of sickness affecting the body or mind
The best doctor prevents illness, an average doctor visits when the illness is imminent, and the unskilled doctor treats your present illness.
From the Old Norse adjective illr (bad, wrong, evil) and the English noun-forming suffix “-ness” (from the Anglo-Saxon –ness/-nyse/-nys) signifying a state or condition).
Thank you to Allen Ward for providing this etymology.