According to Origins, by Eric Partridge:
orient, the east, has late MF-F derivative orienter, whence 'to orient", whence, in part, "to orientate" and, prob after F, orientation; F orienter has the EF-F cpd desorienter. whence "to disorient", largely superseded by "to disorientate", whence disorienattion; hence, anl, "to reorient", now usu reorienatte, whence, anl, reorientation.

Is this any help, or just confusing?