No repeats were found

Question

I am a word, but there only once,
Maybe absurd, perhaps naming some dunce.
Find how they call me, to get the prize,
And solve this riddle, in one or two tries.

What is being talked about?

Hint:

My small aid that can be provided:
Title, Help, Question, all of them, reunited.
After, look, something missing?
Padding, Wording, Definition, forget any red herring.

Another:

This, oh so sought after answer,
Contains simply five letters.
Overanalyzing, here, isn't crime,
Yet some sentences are there just for rhyme.

Answer 1

Partial answer:

What is being talked about, is the fact that:

This puzzle (title, body, and help) contains no repeated words.
The title alludes to this: "No repeats were found".
(If you included the tags, 'Word' is repeated, however).

In terms of finding a specific word or words, a few ideas:
Best guess:

ABSURD
This word appears in the puzzle only once ("there only once"). It literally means absurd ("maybe absurd") and is what you might call a foolish person ("naming some dunce" - 'he is absurd').
"One or two tries" would then clue A=1, B=2, hinting at ABsurd!

Other guesses:

UNIQUE, SINGULAR, and various other words which satisfy three properties: match 'no repeats', synonym for 'absurd', polite name for a dunce. If we restrict to 5 letters, many words also fit these criteria (alone, novel, etc) but none stand out as obviously correct more than the others, so I assume there is another hidden piece to this puzzle?

WORD: interesting as it is the only repeated word, if you consider the tags a part of the puzzle. Hence the 'one or two tries'. The puzzle literally says "I am a WORD"; the rest of the clues would be red herrings.

Answer 2

Are you, maybe, a (new answer)

Number?

I am a word, but there only once,

A number occurs only once.

Maybe absurd, perhaps naming some dunce,

Absurd references imaginary numbers.

Find how they call me, to get the prize,

Seems pretty straightforward.

And solve this riddle, in one or two tries.

One or two tries, the numbers are there!

Answer 3

Because I am dissatisfied with this puzzle, I want to self-answer, also showing my "riddle creation" process. My deepest apologies to the people who tried.

The sough-after word is:

Hapax, or Hapax legomenon. It is a transliteration of Greek ἅπαξ λεγόμενον, meaning "being said once".
Hapaxes are words that appear only once in a body of text, be it book or riddle. An example would be Hebenon, a poison referred to only once in Shakespeare's 'Hamlet'.
As mentioned by @Amoz, every word in this riddle, including hints, is a hapax.

Making of the riddle:

Sadly, the riddle is low-quality, and the first two lines only act as a definition of the word rather than subtle clues to find it. The ability to use proper text in hints became severely limited not only by the constraint of "each word only once", but also the rhyming (which is dubious at best).
I wanted to spread the meaning of the word, as I find it's a term that's not commonly used, yet seems like it would (or should) be.
Line 2 is there to indicate that hapaxes are there for very out-of-place things that only appear once, like a made-up word, or to name someone never encountered before, or called by name afterwards. The second hint was meant to be something to put things back together and prevent straying off the beaten path.