Derived via Latin from the Greek spastikos ("drawing in" or "tugging"), the word spastic refers to an alteration in muscle tone affected by the medical condition spasticity, which is seen in spastic diplegia and many other forms of cerebral palsy and also in terms such as "spastic colon".
Colloquially, spastic can be pejorative; though severity of this differs between the United States and the United Kingdom. In the UK "spastic" is considered by the general population as an offensive way to directly refer to disabled people.
The medical term "spastic" came into use to describe cerebral palsy. The Scottish Council for the Care of Spastics was founded in 1946, and the Spastics Society, an English charity for people with cerebral palsy, was founded in 1951.
However, the word began to be used as an insult and became a term of abuse used to imply stupidity or physical ineptness: one who is uncoordinated or incompetent, or a fool. It was often colloquially abbreviated to shorter forms such as "spaz".
Although the word has a much longer history, its derogatory use grew considerably in the 1980s and this is sometimes attributed to the BBC children's TV show Blue Peter; during the International Year of Disabled Persons (1981), several episodes of Blue Peter featured a man named Joey Deacon with cerebral palsy (described as a "spastic"). Phrases such as "joey", "deacon", and "spaz" became widely used insults amongst children at that time.