This derivation is connected to the legend of Nimrodel. Though the Gilrain was for most of its length a fast, straight river, there was a region about half-way between its source and its mouth where it wandered somewhat, and formed a small mere before flowing on. According to the story, Nimrodel herself wandered beside the river as she descended from the White Mountains, and saw the reflected stars glinting in the mere's waters. She sat beside the pool and slept, and so she did not reach Amroth's ship before it sailed.