I don't recall when/where it came from, but for example the unix mount command uses "path ::= name colon path" delimiting for things like NFS and other "protocol based rather than physical disk" filesystems. And along the lines of what you say, yes it could have been borrowed, but probably from PIP even if it was indirectly via CP/M, Amiga or whatever.
Berners-Lee may have gotten http: from volume naming in the classic MacOS or Amiga, or other systems.
In Unix, devices were always actual bindings in the filesystem space.