I was thinking about the etymology of words like “executor” and “bettor” that use the suffix “-or” to denote the person who performs a verb, instead of the more usual “-er”.
For some reason, it’s never occured to me that “liar” has an even more peculiar construction. Does anyone know the etymology of “liar”? And are there other examples of words with an “-ar” ending? I can’t think of any, but you may do better since I’ve had too many beers and you haven’t. 
Peculiar?
He’s looking for agent nouns. There’s beggar. I don’t hink burglar counts, despite the humorous back-formation burgle. Good question.
Tar? 
OK, agent nouns, as I later edited ;).
According to the OED, the -ar suffix is
So you have beggar, scholar, pillar, and vicar, though they originally ended in -er.
I don’t think scholar, pillar, or *vicar *count, though, because they are not derived directly from verbs. A scholar doesn’t schol, a pillar doesn’t pill, and a vicar doesn’t vic. Most agent nouns end in -er or -or, rather than -ar.
Ooh, beggar and pedlar are excellent examples! And now I’ve learned a new phrase: “agent noun”. Thanks, Ximenean!
Bursar?
And now I want to use Agent Noun as my Doper name!
A word ending with -ar is a sure sign of a loan word from Norse, since the Vikings were pretty good pirrrrrrrates
Somewhat off-topic, but regarding agent nouns ending in -or, I was taught that if you can take the root word and make it end in -ion, the agent noun will end in -or. For example, direction->director, edition->editor. There are, of course, exceptions, but it works a lot of the time.
Registrar
Exemplar.
How about Sarah Michelle Gellar – from a northern Yiddish dialect, no doubt. געללאַר אַנשטאָט פון געללער
Only when she is rocking some Dr. Scholls gel insoles.
Templar?
Yes, he or she does. He or she schools (educates) him or herself. (Probably from the old French escoler).
But I think that “schooler” would be the agent noun derived from the verb “school”, and it would have to mean someone who schools somebody else, rather than somebody who is schooled, otherwise they would be the patient, not the agent. “Scholar” is closely related to “school”, true, but in my book that does make it an agent noun.
I thought of friar, but it does not fit the “agent noun” description since it’s derived from frere.
lets try it out
alligator > allegation
actor > action
equator > equation
hey, it works.