also ingrain, late 14c., originally "dye (a fabric) red with cochineal," from French phrase en graine, from graine "seed of a plant," also "cochineal" (the source of the dye was thought to be berries), thus "fast-dyed." See grain; also compare kermes. Later associated with grain in the sense of "the fiber of a thing." Used figuratively from 16c. Related: Engrained.