1560s, "wild, unruly" (originally in reference to hawks), from French haggard, probably from Old French faulcon hagard "wild falcon," literally "falcon of the woods," from hagard, hagart, from Middle High German hag "hedge, copse, wood," from Proto-Germanic *hagon, from PIE root *kagh- "to catch, seize;" also "wickerwork, fence" (see hedge (n.)). OED, however, finds this derivation "very doubtful." Sense perhaps reinforced by Low German hager "gaunt, haggard." Sense of "with a haunted and wild expression" first recorded 1690s; that of "careworn" first recorded 1853. Sense influenced by association with hag. Related: Haggardly; haggardness.
"lean and haggard," from or as if from hunger, mid-15c. (as a surname from mid-13c.), of uncertain origin; perhaps from a Scandinavian source (compare Old Norse gand "a thin stick," also "a tall thin man") and somehow connected with the root of gander. Connection also has been suggested to Old French jaunet "yellowish" [The Middle English Compendium].
"to pretend illness to escape duty," 1820, from French malingrer "to suffer," a slang word that probably also at one time meant "pretend to be ill," from malingre "ailing, sickly" (13c.), which is of uncertain origin, possibly a blend of mingre "sickly, miserable" and malade "ill." Mingre is itself a blend of maigre "meager" (see meager) + haingre "sick, haggard," which is possibly from Germanic (compare Middle High German hager "thin").
The sense evolution in French would be through the notion of beggars who feigned to be sick or exhibited sham sores to excite compassion. Malingerer is attested from 1761, in a translation of de Saxe; malingering as a verbal noun is attested from 1778. Related: Malingered.