"one who or that which rectifies" in any sense, 1610s, agent noun from rectify.
Entries linking to rectifier
rectify v.
c. 1400, rectifien, "to cure, heal, remedy" (a bad or faulty condition); early 15c. "set (someone) straight in conduct or behavior;" late 15c., "correct an error, set (something) straight or right;" from Old French rectifier, literally "to make straight" (14c.), from Late Latin rectificare "make right, make straight," from Latin rectus "straight" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line") + combining form of facere "to make" (from PIE root *dhe- "to set, put"). Sense of "remove impurities from a distillate" is from mid-15c. Related: Rectified; rectifying.