د ث رd-th-r
— دِثَارdithār: the outer sheet that a person wraps himself in in bed (the opposite of شِعَارshiʿār, which lies next to the body).
Form V (tafaʿʿul) تَدَثَّرَ يَتَدَثَّرُ تَدَثُّرًاtadaththara yatadaththaru tadaththuran: to wrap oneself in a sheet; مُتَدَثِّرmutadaththir ⟵ مُدَّثِّرmuddaththir (the tāʾ has been assimilated into the dāl): one wrapped in a sheet — and from this comes the name of the surah. Only once in the Quran: ﴿يٰٓاَيُّهَا الْمُدَّثِّرُ﴾ (Al-Muddaththir 74:1)