the.com/nightjar

means A nocturnal, insect-eating bird with mottled, bark-like plumage that spends the day motionless on the ground or a branch, camouflaged in plain sight.

from The 'jar' part is the honest bit — it comes from the bird's distinctive churring, jarring song, a rapid mechanical trill it delivers for long stretches at twilight. 'Night' needs no explanation; the bird is crepuscular, most active at dusk and dawn. Older English names leaned into folklore rather than sound: 'goatsucker' (and its Latin genus name, Caprimulgus, means the same) comes from an ancient and false belief, traceable to classical writers, that the bird snuck into barns at night to suckle milk from goats — really it was just hunting the insects stirred up by the livestock. 'Nightjar' won out as the tamer, more accurate name.