From Sherlock Holmes, "The Dying Detective":
He was indeed a deplorable spectacle. In the dim light of a foggy November day the sick room was a gloomy spot, but it was that gaunt, wasted face staring at me from the bed which sent a chill to my heart. His eyes had the brightness of fever, there was a hectic flush upon either cheek, and dark crusts clung to his lips; the thin hands upon the coverlet twitched incessantly, his voice was croaking and spasmodic. He lay listlessly as I entered the room, but the sight of me brought a gleam of recognition to his eyes.
The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
ADJECTIVE: 1. Characterized by intense activity, confusion, or haste: “There was nothing feverish or hectic about his vigor” (Erik Erikson). 2. Medicine Of, relating to, or being a fever that fluctuates during the day, as in tuberculosis or septicemia. 3. Consumptive; feverish. 4. Flushed.
ETYMOLOGY: Middle English etik, recurring, consumptive, from Old French etique, from Late Latin hecticus, from Greek hektikos, from hexis, habit, from ekhein, to be in a certain condition. See segh- in Appendix I.
WORD HISTORY: The Usage Panel survey done for the first edition of the American Heritage Dictionary (1969) found that 92 percent of the Panel approved of the use of hectic in its most familiar sense, “characterized by feverish activity, confusion, or haste.” The question was posed because earlier that sense had sometimes been deprecated as a loose extension of the term's meaning in medicine, “relating to an undulating fever, such as those accompanying tuberculosis.” Without some acquaintance with Middle English one would not recognize the first recorded instance of the word, etik, in a text written before 1398. The Middle English term comes from the Old French development of the Late Latin word hecticus, whose form helped reshape our word in the 16th century. Hecticus comes from Greek hektikos, “formed by habit or forming habit” and “consumptive.” The last sense developed because of the chronic nature of tuberculous fevers. Thus a word that once meant “habitual” eventually had an English descendant used to refer to conditions that most would want to be rare.