Brendan Eich wanted the language be some dialect of Lisp language but his superiors insisted on a language similar to Java. So he wrote that prototype in Common Lisp. It's basically Java like syntax over Common Lisp structs and vectors.
I think Eich was more partial to Scheme than CL, as a model for JS. Though I wouldn’t say it’s Java syntax over either - the scoping rules are very distinct, it’s missing tons of features core to either CL or Scheme, there’s the whole Self-inspired prototype-based OOP layer…
Scheme is a LISP of course, just not Common Lisp.
I have no idea what language the original implementation was in but it makes sense it would be the same as the rest of the browser.
Where did you hear this CL fish story?
It was Waldemar Horwat and js2 https://web.archive.org/web/20111217124744/https://mxr.mozil...