Wiktionary
mousiness
n. The property of being mousy.
Usage examples of "mousiness".
What Blair had initially judged as mousiness was, in actuality, a watchfulness.
Usually she wasn't disturbed by her mousiness, having accepted it as an unchangeable fact, much like having the sun rise in the east.
And it has been my usual experience that all those wildly improbable girls who exist only in the minds of artists appeal chiefly to young men who either know no girls at all, or know only girls of a mousiness equal to their own.
She supposed that his daft mousiness was simply a shield he put up when he was forced to live in the lands of men.