Finance and esoteric languages

Jane Street famously uses OCaml, an otherwise-obscure functional programming language.
Morgan Stanley in the 1970s used APL. (A Demon of Our Own Design by Richard Bookstaber, ch. 3)
Goldman uses a homegrown language called Slang. (HN thread with discussion)
Other big investment banks use "Bank Python", their own homegrown forks of the Python ecosystem.

Anyone know of any other examples?

Outside of finance