1610s, "action of assorting," from assort + -ment. Sense of "group of things of the same sort" is attested from 1759; that of "group of things whether the same sort or not" from 1791.
assortment in Medicine
assortment as·sort·ment (ə-sôrt'mənt) n. The relationship between non-allelic genetic traits that are transmitted from parent to child independently and according to the degree of linkage between the respective loci.