I didn’t realize how long pretzels have been around. See Victoria Emily Jones, Praying with Pretzels.

The salty, twisted treats that we call pretzels have their origin, it is thought, in a seventh-century European monastery—according to lore, either in southern France, northern Italy, or Germany. Allegedly a monk invented them by shaping scraps of leftover bread dough to resemble arms crossed in prayer over the chest.

The pretzel’s Lenten link, not to mention its popularity as a year-round snack both inside and outside monastic communities, led artists to sometimes paint pretzels into Last Supper images.

Illustrations there, one of which I have pinched:

St. Bartholomew, from the Hours of Catherine of Cleves, in Latin, Utrecht, The Netherlands, ca. 1440. Morgan Library, New York: PML M.917, fol. 228. http://www.themorgan.org/collection/hours-of-catherine-of-cleves/87#