You can read about it in detail in Joe Armstrong's master thesis. I would recommend it be read from cover to cover:

http://www.erlang.org/download/armstrong_thesis_2003.pdf

The syntax apparently borrows from Prolog, since the first version was built with Prolog, from what I've read.

Apparently http://delivery.acm.org/10.1145/1240000/1238850/a6-armstrong... , PLEX https://en.wikipedia.org/wiki/PLEX_(programming_language) .

Try to find some of Joe Armstrong's talk on the history. It is pretty interesting. Unlike some academic languages, this one was created by a company with a few set of well defined goals. On of the top ones was high concurrency and fault tolerance. I think they have succeeded and later on, it turns out those same features came to be very useful for concurrent writing large concurrent and fault tolerant services.

So in way it was created from scratch. It has a Prolog like feel but that is superficial only. Prolog was used as the original implementation platform.

It is also interesting they didn't explicitly indent to make a "functional" language or use "actor programming" or "CSP" and so on. Those things fell out of the original requirements of fault tolerance and concurrency.