crap!, shit!; an expression of annoyance, disgust, or exasperation
also merd, "dung," late 15c., from French merde "feces, excrement, dirt" (13c.), from Latin merda "dung, ordure, excrement," of unknown origin. Naturalized in English through 17c., but subsequently lost and since mid-19c. (and especially since World War I) generally treated as a French word when used in English.