The word has several meanings
1. A Diwan is a collection of poems of one author, usually excluding his or her long poems. These poems were often composed and collected in the imperial courts of various sultanates and were very well known for their ability to inspire.
The English usage of the phrase “diwan poetry” comes from the Arabic word diwan, which is loaned from Persian means designated a list or register. The Persian word derived from the Persian dibir meaning writer or scribe. Diwan was also borrowed into Armenian, Arabic, Urdu and Turkish. In Persian, Turkish and other languages the term diwan came to mean a collection of poems by a single author, as in selected works, or the whole body of work of a poet. Thus Diwan-e Mirwould be the Collected works of Mir Taqi Mir and so on. The first use of the term in this sense is attributed to persian/ Tajik port Rudaki.
2. Diwan can also mean minister/tribunal.
Diwan khana – court chamber
Diwan-e ala – prime minister
Diwan-e am – public hall audience
Diwan-e khas – council chamber; cabinet
3. Colloquially an indian style sofa is also called a Diwan. Usually these sofas are lower in hieght with bolsters and cushions placed at the back without a sofa frame as backrest.