Muhammad said: "Huwwah" (darkness) is blackness, and that is why that which is intensely green is called "ahwa" (dark), because it tends toward blackness. "Al-Ghutha'" in the language of the Arabs refers to what you see on the surface of floodwater. It is said of it: "ghatha al-wadi yaghthi" (the valley gathered its debris) when it collects its "ghutha'". The singular of "ghutha'" is "ghutha'ah".
قَالَ مُحَمَّدٌ: الْحُوَّةُ: السَّوادُ، وَلِذَلِكَ قِيلَ لِلشَّدِيدِ الْخُضْرَةِ: أَحْوَى، لِأَنَّهُ يُضْرَبُ إِلَى الْحُوَّةِ. وَالْغُثَاءِ فِي كَلامِ الْعَرَبِ: الَّذِي تَرَاهُ فَوْقَ مَاء السَّيْل، يُقَال مِنْهُ: غثى الْوَادي يغثي إِذا جمع غثاءه، وَوَاحِد الغثاء: غثاءة.
