This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
螈 combines 虫 (insect/reptile) with 原, which likely contributes sound. The exact historical development is uncertain.
The insect radical 虫 beside 原 suggests a creature related to plains or origins, but the meaning is unclear.
For ゲン, imagine a small newt (いもり) named Gen crawling across the plain: Gen -> ゲン.