As introduced by S.G. Howe (1846), simpleton was intended to mean people with mild intellectual disability. However, it never fully entered the worldwide medical community's terminology. The term was later replaced by "moron."
Moron was an invented word. A psychologist named Henry Goddard developed the term. It was used to classify people with mild intellectual disabilities. Goddard created the novel word by combining parts of words like sophomore and oxymoron. The term was used to replace feeble-minded. Feebleminded was misused by society to refer to people with any severity of ID.
Feeble-minded came from the Latin word flebilis. It means, "to be lamented." It referred to people who were not profoundly disabled, but still required intervention and care.
Retarded comes from the Latin retardare. This means, "to make slow, delay, keep back, or hinder." The first record of the word "retarded" in relation to developmental delay was in 1895. The term retarded was used to replace terms like idiot, moron, and imbecile. This was because it was not a derogatory term at that time. However, by the 1960s, the term became a word used to insult someone.
It is interesting to note, that in each case, the original term was neutral in meaning. As the term entered public use, it become pejorative. This fact illuminates social cruelty born of ignorance and fear. There are always competing elements of society. Some of people seek respectful, neutral medical terms. Others misuse these same terms as weapons to insult people.
For health care professionals, diagnostic labels serve as a form of shorthand communication. Diagnostic labels rapidly communicate a set of symptoms associated with a particular condition. It may simultaneously suggest an appropriate treatment. However, when these conditions carry a social stigma, the diagnostic labels themselves become stigmatizing. The original, medical term loses its intended neutral meaning.
In October 2010, President Barrack Obama signed into law a bill known as Rosa's Law. This law required the terms "mental retardation" and" mentally retarded" be stricken from federal records. Instead, these terms were replaced with "intellectual disability" and "individual with an intellectual disability." The most recent version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5, APA, 2013) adopted the term intellectual disability. It replaced the older term mental retardation. This change was due in part to these changes in the law.