1737, "disturbance of regular order," from French dérangement (17c.), from déranger (see derange). Mental sense "disturbance of the intellect or reason" is from 1800.
Entries linking to derangement
derange v.
1776, "throw into confusion, disturb the regular order of," from French déranger, from Old French desrengier "disarrange, throw into disorder," from des- "do the opposite of" (see dis-) + Old French rengier (Modern French ranger) "to put into line," from reng "line, row," from Frankish *hring or some other Germanic source, from Proto-Germanic *hringaz "circle, ring, something curved," from nasalized form of PIE root *sker- (2) "to turn, bend." Mental sense "disorder or unsettle the mind of" is by c. 1790.