BBB Etymology - All Tuckered Out

"Tucker" meaning "to tire, to weary" is an Americanism dating back to the early 19th century, based on the verb "to tuck," which comes from an ancient Germanic root meaning "to pull" (also the source of our "to tug"). By the 13th century tucker had taken on the sense of "to finish cloth" and later came to mean "to gather up in folds or pleats," "to put away or hide" and the modern "to fold in the ends of material" sense we use in "tuck in a sheet."

Midway though the 19th century, it became common to speak of a dog or horse whose flanks were drawn in from hunger or fatigue as being "tucked" or "tuckered," likening the animal's gaunt and haggard appearance to folds in fabric. So to be "tuckered out" today is to be profoundly and visibly exhausted.