Blood libels are allegations that a person or group engages in human sacrifice, often accompanied by the claim that the blood of victims is used in various rituals and/or acts of cannibalism. Its use is nearly always with regard to sensationalized accusations and high emotions. Throughout history, these claims have been frequently made against Jews living in Europe and even resulted in lynching and persecution of whole Jewish communities.
It has recently been used by our modern Mrs Malaprop (she who coined
refudiate last year) Sarah Palin. Pundits say that the reason this phrase has provoked so much anger is because Palin is using the phrase “blood libel” just to refer to verbal criticisms, implying an equivalence between both circumstances. The famous linguist Deborah Tannen has speculated that Palin and her advisors are totally unaware of blood libel’s proper meaning.