A while ago I saw a proposal for a new URL path prefix for website meta files - that is, instead of having everything at root level (like /robots.txt and /favicon.ico) there was a prefix to give /__something_here__/metafilehere
The idea being to give a single prefix to deal with when rewriting/etc for a whole bunch of new meta-files that would live within it (instead of at root level).
I cannot remember what the __something_here__ part is anywhere, and nothing I search for is giving any hint of a clue.
You probably mean /.well-known/.
RFC 5785: Defining Well-Known Uniform Resource Identifiers (URIs):
This memo defines a path prefix for "well-known locations", "/.well-known/", in selected Uniform Resource Identifier (URI) schemes.
Note that such well-known URIs have to be registered before you may use them. Proposals can be made on the mailing list.
All registered well-known URIs are listed here:
http://www.iana.org/assignments/well-known-uris/
(As you’ll see, you can’t use it for your robots.txt or Favicon.)