Is it farther or further?
1850, in both transitive and intransitive senses, from French dérailler "to go off the rails," from de- (see de-) + railler (see rail (n.1)). In general use first in U.S. Related: Derailed; derailing.
To throw off the proper course; wreck: He managed to derail the proposal just before Christmas
[1950s+; The source term, ''To leave or cause a car or engine to leave the railroad tracks,'' was adopted fr French by 1850]