Definition from Wiktionary, the free dictionary
님 (nim) (hanja 任)
- (honorific suffix) esteemed; brother, sister, grandfather
님 (nim) is affixed to many kinship terms to make them honorific, often to refer to family members other than one's own.
- (dependent noun, after a person's name) Mr., Mrs. More respectful than 씨 (ssi).
- 홍길동 님 ― honggildong nim ― Mr. Hong
- (archaic) lord, darling.