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.
<a href="https://www.etymonline.com/word/rectifier">Etymology of rectifier by etymonline</a>
Harper, D. (n.d.). Etymology of rectifier. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/rectifier