Places in Middle-earth
Type: Rivers & Lakes
Meaning: a flowing
Erui, Sirith, Celos, Serni, and Gilrain), land between Ered Nimrais and Ethir Anduin....
Unfinished Tales, Index
sîr 'river', from root sir- 'flow', in Ossiriand..., Sirion; also in Sirannon (the 'Gate-stream' of Moria) and Sirith ('a flowing', as tirith 'watching' from tir), a river in Gondor. With change of s to h in the middle of words it is present in Minhiriath 'between the rivers'...; in Nanduhirion 'vale of dim streams', the Dimrill Dale..., and in Ethir Anduin, the outflow or delta of Anduin (from et-sir).
The Silmarillion, Appendix: Elements in Quenya and Sindarin Names
In at least one earlier, black and red version of the Map of Middle-earth from The Lord of the Rings, the names of the rivers Celos and Sirith are switched. The similar Map of Gondor, however, shows them in the correct order, and the map above has been corrected. The Celos is, in fact, to the west (left) of the Sirith, closer to the Gilrain/Serni system, as confirmed by the following passage:
The Gilrain came swiftly down from the mountains as did the other rivers of that region; but as it reached the end of the outlier of Ered Nimrais that separated it from the Celos... it ran into a wide shallow depression.
Unfinished Tales, Part 2, Ch 4, The History of Galadriel and Celeborn: Amroth and Nimrodel
Still Anonymous, 5Mar04
Elena Tiriel 31Aug10