Etymology of Professor
A professor is defined by most dictionaries as a high ranking or highly educated teacher, usually actively teaching in a university. In North America, university teacher is used more than university professor.
The etymology of the word professor starts with the Latin verb profiteri (declare, profess). To understand the origin of this word, we have to look at how this verb is conjugated in Latin. It’s fairly simple: in the indicative perfect, the indicative future perfect, the indicative pluperfect, the subjunctive pluperfect, and the subjunctive perfect, the word profiteri changes into either professus or professi. This then became, in Latin, the nominative and singular, professor (plural: professores).
The implied meaning is that he or she who professes is a professor.
Middle English already used the word professor. The first written record of this word was found in the late fourteenth century. Anglo-Norman: proffessur.
It’s important not to confuse the word professor with the words teacher, instructor, trainer, coach or tutor.
A teacher, by definition, is someone who teaches. This will usually be a school teacher, but there are teachers in all walks of life. You can have a meditation teacher, for instance.
An instructor is somebody who instructs, and this usually involves some kind of physical skill, which is why you have yoga instructors, not yoga teachers.
A trainer is an individual who trains you in very specialized skills, usually for the purpose of getting a job.
A coach is a man or woman who coaches you. While this word has usually been reserved for sports (for example, a football coach), this isn’t the case anymore. For instance, life coaches are very popular nowadays.
A tutor is somebody who gives private lessons (usually in exchange for money). For example, a private English tutor in London can charge a very respectable amount of money for his services.
Murray, John. An Etymological Dictionary of Modern English. 1921.