divan:  The word divan has a long and spectacularly variegated semantic history. It started out as Persian dēvān, which originally meant ‘small book’. This came to be used specifically for ‘account book’, and eventually for ‘accountant’s office’. From this its application broadened out to cover various official chambers and the bodies which occupied them, such as tax offices, customs collectors, courts, and councils of state.
And finally it developed to ‘long seat’, of the sort which lined the walls of such Oriental chambers. The word carried these meanings with it via Arabic dīwān and Turkish divān into the European languages, and English acquired most of them as a package deal from French divan or Italian devano (it did not, however, include the ‘customs’ sense which, via the Turkish variant duwan, survives in French douane, Italian dogana, Spanish aduana, etc).
The 19th-century sense ‘smoking lounge’ seems to be an exclusively European development.
1580s, "Oriental council of state," from Turkish divan, from Arabic diwan, from Persian devan "bundle of written sheets, small book, collection of poems" (as in the "Divan i-Hafiz"), related to debir "writer."
Sense evolved through "book of accounts," to "office of accounts," "custom house," "council chamber," then to "long, cushioned seat," such as are found along the walls in Middle Eastern council chambers (see couch). The sofa/couch sense was taken into English 1702; the "book of poems" sense in 1823.