1540s, "to disgrace," of uncertain origin. Perhaps a Scottish respelling of bauchle "to disgrace publicly" (especially a perjured knight), which is probably related to French bafouer "to abuse, hoodwink" (16c.), possibly from baf, a natural sound of disgust, like bah (compare German baff machen "to flabbergast"). The original sense is obsolete. Meaning "defeat someone's efforts, frustrate by interposing obstacles or difficulties" is from 1670s. Related: Baffled; baffling.
"shielding device," especially in a stove or oven, 1881 (short for baffle-plate), from baffle (v.). Earlier in the same sense was baffler (1861).