late 14c., "to boil partially;" mid-15c., "to boil thoroughly," from Old French parboillir "to boil thoroughly," from Medieval Latin perbullire "to boil thoroughly," from Latin per "through, thoroughly" + bullire "to boil" (see boil, v.). Main modern meaning "boil partially" is by mistaken association of the prefix with part. Related: Parboiled; parboiling.