"to treat ill, abuse," 1708, from French maltraiter, or formed in English from mal- + treat (v.). Related: Maltreated; maltreating.

"one who is ill-behaved," mid-15c., especially "lascivious, lewd person" (1520s), from wanton (adj.).

"to govern ill, administer unfaithfully," c. 1400, misgovernen, from mis- (1) "badly, wrongly" + govern. Related: Misgoverned; misgoverning.

mid-15c., "somewhat ill," from un- (1) "not" + well (adj.). Similar formation in North Frisian unwel, German unwohl.

"disease, sickness, ailment, malady," 1680s, from ill (adj.) + -ness. Earlier it meant "bad moral quality" (c. 1500).

certificate that a student is ill, Latin, literally "he is sick," third person singular of aegrotare "to be sick," from aeger "sick."

also sick-bed, "bed upon which one lies ill," early 15c., from sick (adj.) + bed (n.).

"erring in purpose or action," 1650s, past-participle adjective from misguide (v.). Earlier, "ill-behaved" (late 15c.). Related: Misguidedly; misguidedness.

"anything that befalls of ruinous or distressing nature; any unfortunate event," especially a sudden or great misfortune, 1590s, from French désastre (1560s), from Italian disastro, literally "ill-starred," from dis-, here merely pejorative, equivalent to English mis- "ill" (see dis-) + astro "star, planet," from Latin astrum, from Greek astron "star" (from PIE root *ster- (2) "star").

The sense is astrological, of a calamity blamed on an unfavorable position of a planet, and "star" here is probably meant in the astrological sense of "destiny, fortune, fate." Compare Medieval Latin astrum sinistrum "misfortune," literally "unlucky star," and English ill-starred.

also heart-sick, "despondent," late 14c., from heart (n.) + sick (adj.). Old English heortseoc meant "ill from heart disease."