Early 18th century; earliest use found in William Derham (1657–1735), Church of England clergyman and natural philosopher. Origin uncertain; perhaps the same word as nidiot, nidget (although the semantic development is difficult to account for), or perhaps connected with midget, or perhaps connected with nidget to provide or seek assistance for a woman in labour (although this is also first attested later), perhaps through the notion of acting as an assistant.