Here churning is a mistake; we are sorry to begin with an animadversion, but the word should be churring.
And out of the distance the nightjar set again to its churring.
The churring of the night-hawks was continuous, soothing as the hum of a spinning-wheel.
A night-jar was spinning; the churring sound affected him oddly.
c.1600, echoic of a grasshopper's trill. Related: Chirred; chirring.