"scientific discrimination," especially in pathology, "the recognition of a disease from its symptoms," 1680s, medical Latin application of Greek diagnosis "a discerning, distinguishing," from stem of diagignoskein "discern, distinguish," literally "to know thoroughly" or "know apart (from another)," from dia "between" (see dia-) + gignoskein "to learn, to come to know," from PIE root *gno- "to know."
