Fully Qualified means that whatever it is has all the qualifications which are applicable. This could mean a qualification such as an FQDN has:
2 not complete or absolute; limited
That is, a fully-qualified domain name is limited to a specific domain, and that limitation in scope is sufficiently stringent to make it unambiguous.
But they could be academic or vocational qualifications:
1 officially recognized as being trained to perform a particular job; certified
In these cases one would not talk of an "unambiguous carpenter".