gaunt

First recorded in 1400–50; late Middle English, probably from Old French gaunet, jaunet “yellowish,” derivative of gaune, jaune “yellow,” from Latin galbinus “greenish-yellow”

1. See thin.

Gaunt was originally used to mean “slim, slender.” Until the early 18th century, this now obsolete sense existed alongside the current sense “extremely thin and bony.”
The etymology of gaunt is uncertain. It is a Middle English word (also spelled gant ) that may come from Old French gant, a possible variant of gaunet, jaunet “yellowish.” Other etymologists suggest a Scandinavian origin, such as Norwegian gand “a thin, pointed stick; a tall, thin man.”
John of Gaunt, a son of King Edward III and father of King Henry IV, was so named because he was born in the Flemish city of Ghent ( Gand in French, Gent in Flemish), corrupted to Gaunt in English.

C15: perhaps of Scandinavian origin; compare Norwegian dialect gand tall lean person