It is not common
It is atypical.
Old English Synonyms
The quality of being unusual; strangeness.
There is no definitive answer to this question as the interpretation of the word ‘unusualness’ may vary from person to person. In general terms, ‘unusualness’ could be described as the state or quality of being different from what is usual, typical or expected.
1. There is an unusualness about his behavior that I can’t quite put my finger on.
2. The unusualness of the situation made it all the more difficult to deal with.
3. I was struck by the unusualness of her appearance.
4. The unusualness of the circumstances made it difficult to know how to respond.
5. There was an unusualness to his manner that made me uneasy.