Blanche \b-lan-che, bl(a)-nche\ as a girl's name is of Old French and Old German origin, and the meaning of Blanche is "white, pure". Originally a nickname for a blonde, "blanc". It became associated with whiteness as in purity, and beauty. It was introduced into England as a given name by the Normans. Blanche DuBois is a character in Tennessee William's "A Streetcar Named Desire".
For more information, see also the related name Candida.