Avenger of Blood
(The) The man who, in the Jewish polity, had the right of taking vengeance on him who had slain one of his kinsmen. The Avenger in Hebrew is called goël.
Cities of refuge were appointed for the protection of homicides, and of those who had caused another's death by accident. The Koran sanctions the Jewish custom. Family feuds have been a common hunting ground of poets and novelists.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894