- ill
- c.1200, "morally evil" (other 13c. senses were "malevolent, hurtful, unfortunate, difficult"), from O.N. illr "ill, bad," of unknown origin. Not related to evil. Main modern sense of "sick, unhealthy, unwell" is first recorded c.1460, probably related to O.N. idiom "it is bad to me." Illness "disease, sickness" is from 1689. Slang sense of "very good, cool" is 1980s.