Onomastics
In Japanese the river is called Kamo-gawa, officially written using the kanji compound 鴨川. The first kanji means "wild duck" and is read kamo, and the second kanji means "river" and is read gawa. However, other kanji applied to this name are 賀茂川 or 加茂川. The first appearance in historical documents of the kanji 賀茂川 is in the Yamashiro no kuni fudoki (山城国風土記). In an entry dated the 19th day of the 6th month of 815 in the history Nihonkiryaku (日本記略), it is referred to as 鴨川. Now, the river north of where it joins with the Takano River is usually distinguished as the 加茂川 when written in kanji, and the river south of there is distinguished as the 鴨川.
The geographical area called Kamigamo, around the mouth of the valley leading into the Kyoto Basin, became the home grounds of the Kamo (賀茂) clan in ancient times. From this, there arose the regional name Otagi Region Kamo Block (愛宕郡賀茂郷), and consequently the geographical name Kamo (賀茂) set down roots. The river name took after this geographical name.
From the Deai Bridge until the Iwaya Bridge north of Kyoto city it is called Kumogahatagawa (雲が畑川) as it passes through the Kumogahata village. North of the Iwaya Bridge until its source the Kamo River is known as Ojitanigawa (祖父谷川).
Read more about this topic: Kamo River