ETYM Old Eng. defoulen, -foilen, to tread down, Old Fren. defouler; de- + fouler to trample, and Old Eng. defoulen to foul (influenced in form by the older verb defoilen). Related to File to defile, Foul, Defoul.
To place under suspicion or cast doubt upon; SYN. sully, corrupt, taint, cloud.