If you see someone who’s been through such a physically exhausting or draining experience that they look gaunt, tired, spent, anxious, and fatigued, that person looks “haggard.” At least that’s how they’d be described nowadays.
“Haggard” has been around for quite a few centuries, and it’s one of those words that’s shifted in meaning pretty significantly. When it first arrived from French around the early 1500s, it was a very specific term used in falconry, and meant a young falcon or hawk that had been captured, but not yet trained. The sport of falconry still exists (barely) and in that obscure corner, “haggard” still keeps its original meaning. But it’s fairly obscure even within falconry, which itself is pretty obscure, and that makes it vanishingly rare.
By the late 1500s, “haggard” began to be applied to people. But not in the way we use it today. Sensibly enough, if a person seemed to be as wild and untrained as a young hawk, that’s when they’d be called “haggard.” Robert Cawdry defined it in a sort of dictionary published in 1609: “Hagard, wilde, strange, contrary.”
Shakespeare, as he liked to do, used “haggard” in a double sense in Othello: “If I do prove her haggard, / Though that her jesses were my dear heartstrings, / I’d whistle her off and let her down the wind / To prey at fortune.” Here he’s comparing Desdemona (his wife) to an actual hawk, and also wondering how “untamed” or uncontrollable she might be.
The next way “haggard” came to be used was to refer to somebody who looks starved: “The gaunt, hagard forms of famine and nakedness.” That’s from 1796. It’s not clear how the jump from “wild” to “starving” made sense, but maybe in polite society the idea was that the only reason to be untamed or unsociable was that there was something wrong with you. Given the times, a likely culprit was probably starvation.
From there, “haggard” began to be used to mean unwell in any sense, but particularly because of advanced age. “To prevent the haggard look which comes upon women who grow thin at fifty.” That’s from 1840, when I suppose 50 was probably considered advanced age. The theory about why “haggard” began to take on this meaning revolves around the possibility that people thought “haggard” was related to the word “hag” (it’s not). The majority of the citations for this version of “haggard” do, in fact, refer to women.
“Hag,” by the way, is a much older word based on the Old English “hægtesse”, which meant either a witch or a supernatural evil spirit that happened to be female.
Anyway, the modern meaning of “haggard” showed up in the 1800s, and all the others dropped away (except among falconers, of course). Charlotte Brontë used it in the modern way in Villette, from 1853: “Thin, haggard, and hollow-eyed; like a sitter-up at night.” Or, of course, like somebody subjected to far too much trivia about the history of English words.