I'm a little confused by the phrase "one of the only" – as far as I can tell, it just means the same as "one of the" with the vague implication that the number of things in the set is relatively small.
For example, "Neil Armstrong is one of the only men to land on the moon." It sounds like he's one of the few men to do this, just without using the word "few". Because then it's obvious that you're using the vague word "few" and not saying what it means.
"He is the only man to do this" – that's clearly saying that only one person has ever done it.
"A, B and C are the only people to do this" – again, that's clear, there are only 3.
"A is one of only 10 people to do this" – clear. There are 10 in the set, and A is one of them.
"He is one of the only people to do this" – doesn't seem to say anything at all. He's not the only one, but there is no clue whether 3 people have done it or 3 million.
"He is one of the few people to do this" / "He is one of the people to do this" – not clear, but at least it's clear that it's not clear. If you see what I mean. It's not trying to sound like it's saying something when it's not.
Or does "one of the only" actually have some specific meaning?
Best Answer
In my experience it's a way of indicating how extremely rare the 'thing' is.
To use your example of "One of the only people to" ... vs "One of the few people to...". Both phrases indicate that more than one person did the 'thing' but that not many people did the 'thing'.
Using the former phrase is a way to add emphasis and an indication of the level of difficulty or challenge associated with the 'thing'. For example I would use the following in conversation:
"He is one of the only men to land on the moon" vs "He is one of the few people to orbit the earth"
Landing on the moon is much more rare, and difficult, than orbiting the earth. Of course, orbiting the earth is still rare, and difficult.
My opinion or interpretation - don't think you'll find a definitive answer.
Regards