Professor of nothing

A professor of nothing is a fallacy that occurs when a source is introduced as a "Professor" or "Doctor" or similar (and thus authoritative), yet either they are not a professor or doctor or their field of expertise is not the topic at hand.

The fallacy is an argument from authority and thus a conditional fallacy.

Examples
The vast majority of the "positive" reviews of Michael Cremo's Forbidden Archeology: The Hidden History of the Human Race are introduced as "Dr." yet are not qualified to speak authoritatively on archaeology.

Young Earth creationist Ian Juby has also occasionally been introduced as "Professor Juby", at least by Carl Baugh, despite not having any semblance of qualification in paleontology (or any other scientific field).

Problems
Simply put, if someone's not an expert in a field, they can't be cited as one.

Every time an "expert" is touted with a title but without their area of expertise, be wary. If the quoter cannot provide the field in question, the source's authority can also be questioned.

Poem
Dennis Earl's poem, Professor Nothing, despite implications of conspiracy, covers some of the problems with supposed experts: