The term imbecile was once used by psychiatrists to denote a category of people with moderate to severe intellectual disability, as well as a type of criminal. The word arises from the Latin word imbecillus, meaning weak, or weak-minded. It included people with an IQ of 26–50, between "idiot" (IQ of 0–25) and "moron" (IQ of 51–70). In the obsolete medical classification (ICD-9, 1977), these people were said to have "moderate mental retardation" or "moderate mental subnormality" with IQ of 35–49.
The meaning was further refined into mental and moral imbecility. The concepts of "moral insanity", "moral idiocy"," and "moral imbecility", led to the emerging field of eugenic criminology, which held that crime can be reduced by preventing "feeble-minded" people from reproducing.
"Imbecile" as a concrete classification was popularized by psychologist Henry H. Goddard and was used in 1927 by United States Supreme Court Justice Oliver Wendell Holmes Jr. in his ruling in the forced-sterilization case Buck v. Bell, 274 U.S. 200 (1927).
The concept is closely associated with psychology, psychiatry, criminology, and eugenics. However, the term imbecile quickly passed into vernacular usage as a derogatory term, and fell out of professional use in the 20th century in favor of mental retardation.
Phrases "mental retardation", "mentally retarded", and "retarded" are subject to the euphemism treadmill: initially used in a medical manner, they gradually took on derogatory connotation, just as did earlier synonyms (for example, moron, imbecile, cretin, dolt and idiot, formerly used as scientific terms in the early 20th century), leading to a search for connotatively neutral replacements. In the United States, "Rosa's Law" changed references in many federal statutes that referred to "mental retardation" to refer instead to "intellectual disability".
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- World Health Organisation (1977). Manual of the International Statistical Classification of Diseases, Injuries, and Causes of Death (PDF). Vol. 1. Jeneva. p. 212.
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- Fernald, Walter E. (1 April 1909). "The imbecile with criminal instincts". American Journal of Psychiatry. 65(4):731–749.
- Rafter, Nicole Hahn (1998). Creating Born Criminals. Urbana, Ill.: University of Illinois Press. ISBN 978-0-252-06741-9.
- Tredgold, A. F. (1921). "Moral Imbecility". Proc R Soc Med, 1921; 14(Sect Psych): 13–22.
- Goddard, Henry Herbert (1915). The Criminal Imbecile; an Analysis of Three Remarkable Murder Cases. New York: The Macmillan Company.
- Lombardo, Paul A. (2008). Three Generations, No Imbeciles: Eugenics, the Supreme Court, and Buck V. Bell. JHU Press, ISBN 978-0-8018-9010-9
- Kaplan, Robert M.; Saccuzzo, Dennis P. (2008). Psychological Testing: Principles, Applications, and Issues. Cengage Learning, ISBN 978-0-495-09555-2
- Sweet, Lynn (October 5, 2010). "Obama signs 'Rosa's Law;' 'mental retardation' out, 'intellectual disability' in Archived January 17, 2013, at the Wayback Machine.". Chicago Sun-Times.