cast aspersions,

To make a derogatory or highly critical remark, either fairly or, more often, unfairly. An older meaning of the verb “to asperse” is to sprinkle or scatter, and “aspersion” itself once meant a shower or spray. The full phrase is newer, but we find the same meaning in Sheri- dan’s play, The Rivals (1775), in which Mrs. Malaprop complains bitterly of “an attack upon my language! . . . an aspersion upon my parts of speech” (3:3).