"tie or fastening to keep a stocking in place on the leg," early 14c., from Old North French gartier "band just above or below the knee" (Old French jartier, 14c., Modern French jarretière), from garet/jaret "bend of the knee," perhaps from Gaulish (compare Welsh garr "leg").
Garter in reference to the highest order of knighthood (mid-14c.) is from the Order of the Garter, the earliest records of which are entirely lost, but which according to Froissart was established c. 1344 by Edward III, though the usual story of how it came about is late (1614) and perhaps apocryphal. Garter-snake (1773) said to be so called from some fancied resemblance to a ribbon. Garter belt attested by 1913.