What's the meaning of the phrase 'Date rape'?
Rape by an acquaintance during a social engagement.
What's the origin of the phrase 'Date rape'?
This term is of American origin. The earliest example that I have found of it in print is from The Indiana newspaper the Anderson Daily Bulletin, November 1973:
When the study commission gets to the rape laws, Wilson [Judge John Wilson Jr.] said he will propose laws dealing with various degrees of rape to distinguish "date rape from stranger rape."