in reference to the branch of Turks which founded and ruled the Ottoman Empire, 1580s (n.), c. 1600 (adj.), from French Ottoman via Italian Ottomano, ultimately from Arabic 'Uthmani "of or belonging to 'Uthman," Arabic masc. proper name, which in Turkish is pronounced Othman (see Osmanli). The founder of the dynasty reigned 1259-1326. Because -i was a plural inflection in Italian, the ending of the word was altered by formation of a new false singular. Byron used the more correct form Othman (perhaps for the sake of metrics as well as accuracy), and a few writers have followed him.
The type of couch or cushioned seat without back or arms (used in drawing-rooms and sitting-rooms) was so called by 1806, because one reclines on it, which was associated with Eastern customs (see couch (n.1)). By 1849 the word was extended to a small version of this used as a footstool or low seat.