Swedish SL started about 1800. Wittmann (1991) proposes that it descends from British Sign Language. However, other sources state that Swedish SL has no known predecessor. Regardless, Swedish SL in turn gave rise to Portuguese Sign Language (1823) and Finnish Sign Language (1850s), the latter with local admixture; Finnish and Swedish Sign are mutually unintelligible.
^a Sign-language names reflect the region of origin. Natural sign languages are not related to the spoken language used in the same region. For example, French Sign Language originated in France, but is not related to French.