The origin of the name Niger stares us in the face but remains un-coded due to a deep rooted bias against this powerful tool- the Sanskrit language. Lets therefore turn west then and look at Ptolemy's analysis of the name Niger. In his writings Ptolemy mentioned two rivers in the desert of NIger, one by the name 'Gir' and farther south, the 'Ni-Gir''. Roman historian, Suetonius (69-122 AD) wrote that the name 'gher' originates from the Bereber language, spoken in Morocco and Algeria and means 'watercourse'.
But it is obvious that the word 'gir' is a distortion of the same Sanskrit word that appears in the names of rivers around the word. The word is 'jhara', and appear in the names of many rivers and water bodies around the world such as the 'Jari' which is the northern tributary of the River Amazon, River Jara in Melbourne, the Jara River (a tributary of the Susita River) in Romania, or Lake Jara in New Mexico - not to mention many more in India and Nepal. In Sanskrit the word 'jhara' (झर) means a waterfall or a water body, and 'jhari' (झरी) means a river.
Popular explanations include explanations such as that the name Niger is a distortion of the local Tuareg phrase 'gher n gheren' which means 'river of rivers', and the belief is that 'gher n gheren' has been shortened to 'ngher'. However, the analysis gets a little more interesting if one were to decode 'gheren' and 'gher' and 'gheren', or the cognates of these two words, with the help of Sanskrit.
First of all 'gheren' may again be a distortion 'jhara' itself. Or then there is 'gehevra' (गह्वर) or 'gehena' (गहन), both meaning 'deep'. Uncannily, it is the Hindi 'ghehra' (गहरा), also derived from Sanskrit 'gehevra' (गह्वर), which phonetically comes closest to the Tuareg word 'gheren'.
River Niger, which is the third longest in Africa, flows through both Nigeria and Niger. Though Nigeria is full of water bodies and waterfalls, a vast majority of the Niger land is essentially dry and arid. Lets look at its name.
Nira (नीर) means water. However, 'Na' or 'ni' (न) means 'not or 'no'. 'Jhar' (र्झर) by itself means 'flowing water'. So a civilization somewhere on the ancient time line of Africa might have named this neighbouring area of NIgeria as Niger (निझर), which means 'Without Water' - it after all aptly describes the arid topography of Niger.
With time and change in pronunciation, and the impact of rising and falling civilizations, we today are left with the slightly distorted 'Nigeria' and 'Niger' from their original form in Sanskrit, but the essence of their meanings is still there!