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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.