أدب

Probably back-formed singular from آدَاب (ʔādāb), a plural of the verbal noun دَأْب (daʔb), “persistence, perseverance”. (For the plural type, compare آبَار (ʔābār, “wells”), آثَار (ʔāṯār, “revenges, retaliations”), آرَاء (ʔārāʔ, “views, opinions”). Various influences from Iranian at least for semantics are often claimed, surely inspired by some general idea of Abbasid cultural supremacy, and present Iranian patriotism hurt by the pervasiveness of Arabic-origin words in the Persian tongue.