mid-15c., disacordaunce, "lack of agreement," from Old French desacordance, from desacorder (see disaccord). Related: Disaccordant.
early 15c., "want or lack of anything," especially lack of something essential to perfection or completeness, from Old French defect and directly from Latin defectus "failure, revolt, falling away," noun use of past participle of deficere "to fail, desert," from de "down, away" (see de-) + combining form of facere "to do, make" (from PIE root *dhe- "to set, put").
1520s, "lack of regular arrangement;" 1530s, "tumult, disturbance of the peace;" from disorder (v.). Meaning "an ailment, a disturbance of the body or mind" is by 1704.