This term was coined by the US Democratic National Committee in the early 1980s as a more acceptable term than handicapped (or, in the UK, disabled). The motivation seems to have been both a genuine attempt to view the people previously called handicapped in a more positive light and also as need to be seen as politically correct. The Los Angeles Times reported it this way in 1985:
"In a valiant effort to find a kinder term than handicapped, the Democratic National Committee has coined differently abled. The committee itself shows signs of being differently abled in the use of English."