The dorhawk or nightjar.
any of a family (Caprimulgidae) of goatsuckers; esp., the common European nightjar (Caprimulgus europaeus)
Origin of nightjarnight + jar: from the whirring noise made by the male
Any of various chiefly nocturnal, insectivorous birds of the family Caprimulgidae, especially those in the genus Caprimulgus. Also called goatsucker.
Origin of nightjarnight + jar2 (from their harsh calls).