A busybody, do-gooder, meddler, or marplot is someone who meddles in the affairs of others.
An early study of the type was made by the ancient Greek philosopher Theophrastus in his typology, Characters, "In the proffered services of the busybody there is much of the affectation of kind-heartedness, and little efficient aid."
Susanna Centlivre wrote a successful play, The Busie Body, which was first performed in 1709 and has been revived repeatedly since. It is a farce in which Marplot interferes in the romantic affairs of his friends and, despite being well-meaning, frustrates them. The characterisation of Marplot as a busybody whose "chief pleasure is knowing everybody's business" was so popular that they appeared as the title character in a sequel, Marplot. The name is a pun — / plot — and passed into the language as an eponym or personification of this type.
In English law, the doctrine of locus standi requires that a plaintiff have some connection with the matter being contested. In two cases in 1957 and 1996, Lord Denning ruled that "The court will not listen to a busybody who is interfering in things which do not concern him..." Similarly, there is a long-standing rule that a person must have an insurable interest in a property or person that they wish to insure.