wraith
n. countablen. a ghost or a spirit of a person that people see shortly before or after they die. It can also describe someone who looks very thin, pale, and weak.
n. an apparition or ghostlike image of someone, especially one seen shortly before or after their death. Often used figuratively to describe a person who has become emaciated or pale due to illness.
The old stories tell of a wraith that haunts the castle ruins.
After weeks of illness, he looked like a wraith of his former self, pale and barely able to stand.
The poet described the morning mist as a collection of silver wraiths rising from the lake, vanishing as soon as the first rays of sunlight touched the water's surface.
Borrowed from Middle Scots wraith, first attested in 1513 in a translation of the Aeneid. The word has no certain etymology; it may be a transferred use of Middle Scots wraith, wrath (nominally "anger, rage", adjectivally "angry, wrathful"), thus connecting it to writhe and making it a doublet of wrath and wroth. Century Dictionary compares Old Norse vǫrðr (“guardian”); Klein compares Irish arrachd (“apparition”), which is related to riochd (“shape, likeness”).
Often used in the fixed phrase 'a wraith of one's former self' to describe extreme physical decline.