“Divan” is one of the most complicated words I know. The American Heritage Dictionary gives the following definitions:
1. A long backless sofa, especially one set with pillows against a wall.
2. a. A counting room, tribunal, or public audience room in Muslim countries. b. The seat used by an administrator when holding audience. c. A government bureau or council chamber.
3. A coffeehouse or smoking room.
4. A book of poems, especially one written in Arabic or Persian by a single author.
The OED adds the meaning ‘a room having one side entirely open towards a court, garden, river, or other prospect’ and expands on the fourth sense as follows: “A Persian name for a collection of poems (Persian, Arabic, Hindustani, Turkish); spec. a series of poems by one author, the rimes of which usually run through the whole alphabet. [From the original sense ‘collection of written sheets’, perh. influenced by later uses of the word.]” And speaking of “original sense,” check out the etymology: