An establishment whose main business is the sale of chocolate as a hot drink.
Chocolate houses were much frequented in the 18th cent. (after which chocolate declined in popularity and fashionability as a drink), and were known as places for the exchange of political and literary conversation, news, etc..
Origin
Late 17th century; earliest use found in William Mountfort (c1664–1692), actor and playwright. From chocolate + house, after coffee-house.