What word or phrase does your mother always say?
1640s, from Latin rancidus "rank, stinking, offensive" (also source of Italian rancido, Spanish rancio), from rancere "be spoiled or rotten," of unknown origin. German ranzig is from French rancide. Related: Rancidness.
rancid ran·cid (rān'sĭd)
Having the disagreeable odor or taste of decomposing oils or fats.