Rennellese Sign Language is an extinct form of home sign documented from Rennell Island in the Solomon Islands in 1974. It was developed about 1915 by a deaf person named Kagobai and used by his hearing family and friends, but apparently died with him; he was the only deaf person on the island, and there never was an established, self-replicating community of signers. Accordingly, in January 2017 its ISO 639-3 code [rsi] was retired. Kuschel, the only source of information about this communication system, cites no evidence to suggest that there was any contact with any sign language.
References
Kuschel, Rolf (1974). A Lexicon of Signs from a Polynesian Outliner Island: A Description of 217 Signs as Developed and Used by Kagobai, the Only Deaf-Mute of Rennell Island (PDF). København: Københavns Universitet. pp. 187 pages. ISBN 9788750015062. Retrieved 2016-01-22. 9788750015062 ↩
"ISO 639-3 Registration Authority Change request documentation for: 2016-002". ISO 639. SIL International. Retrieved 1 February 2017. http://www-01.sil.org/iso639-3/chg_detail.asp?id=2016-002&lang=rsi ↩
Kuschel, Rolf (1974). A Lexicon of Signs from a Polynesian Outliner Island: A Description of 217 Signs as Developed and Used by Kagobai, the Only Deaf-Mute of Rennell Island (PDF). København: Københavns Universitet. pp. 187 pages. ISBN 9788750015062. Retrieved 2016-01-22. 9788750015062 ↩